How does Covid impact MLB players’ performance? What athletes, trainers and the stats say
As spring training (and the rest of America) shut down around him in March 2020, Jed Lowrie rented a car to drive home to Houston. He started feeling bad on the drive, and tested positive for Covid the next day.
“It was scary to me because I had the lower respiratory stuff,” Lowrie recalled of getting Covid in those pre-vaccine days, when he was with the Mets. “I couldn’t take a full breath. I was at 50 percent of my lung capacity. I had a fever for two days, but that wasn’t the worst part — it was the breathing. It was pneumonia-like symptoms. The lack of being able to get air into my lungs. I don’t think I did anything baseball-wise. Baseball was the last thing on my mind, quite frankly.”
He said it was two months before he could do a workout “that approximated what I was doing before.” The world has changed since then, and Lowrie has gotten vaccinated and boosted. And then, this spring, while playing for the A’s, he got Covid again. His experience was better, but he is a professional athlete, and returning immediately to peak performance after a bout with the illness is still no simple task.
“This year, it was three days where I felt pretty bad, another two weeks where I had some brain fog, and was forgetting things easily. I was getting some fatigue for a while. I was out for ten days. It probably took another ten days after we got back to feel fully right,” said Lowrie, who went 5-for-34 and saw his OPS plummet from .748 to .511 in the two weeks after returning from the COVID-19 IL.
Because the severity of the health outcomes for most of the general public is so much better after the vaccine, it might be tempting to shrug off Covid as it becomes endemic. But even the most athletic among us are reporting issues with fatigue that can stretch long after the last days of traditional flu-like symptoms.
In a study that included 71 hitters and 61 pitchers who were confirmed to have had Covid, The Athletic found that performance was well down from expectations in the first two weeks back off the injured list.
In the sample population, in the first fifteen days off the IL:
- Hitters’ median OPS went down 63 points compared to pre-season projections
- Pitchers’ median ERA went up 11 points compared to pre-season projections
- 69 percent of the pitchers lost velocity compared to the 15 days before
- Median velocity loss was 0.4 mph
- 54 percent of the hitters lost exit velocity compared to the 15 days before
- Median exit velocity loss was 0.6 mph
In the current transition from the more harrowing early days of the pandemic, there are going to be differences and inequalities — between countries, between socioeconomic classes, between people with underlying conditions that make them more susceptible to worse outcomes — and those can lead to vastly different viewpoints on the virus. Athletes, who are young and perhaps more likely to shrug off the risks of the virus, have publicly shared a range of opinions, and seen their responses heavily scrutinized and politicized.
But now we are starting to see evidence that even a vaccinated professional athlete can be laid low by Covid and feel the effects for a while after the symptoms have abated. To put that top-line finding in context, a 63-point OPS loss compared to preseason projections is worse than the post-IL outcomes for an injury to any single body part.
(Injury data courtesy of Derek Rhoads and Baseball Prospectus)
“Definitely my body hasn’t felt the same after the virus,” Yoan Moncada of the White Sox told The Athletic’s James Fegan after his bout with the virus in 2020. “I feel a lack of energy, strength, it’s just a weird feeling. It’s different. When I got to Chicago before I tested positive, I was feeling strong and with energy. Now, it’s like a daily battle to try to find that strength, that energy to go through the day. But I think that’s something that I have to deal with and it is what it is. I have to find a way to get through it.”
Some of what Moncada reports is consistent with what is often termed “long Covid,” since he struggled for much of 2020 with symptoms, and the CDC defines long Covid as any recurring and ongoing symptoms four weeks after infection. But there are also some examples of what could be called medium cases, which lead to outcomes that even this study would fail to capture.
After the Mariners’ Mitch Haniger tested positive in mid-April, he had a fever and chills for three to four days with a slight cough and congestion. But then, as a secondary result of the virus, he got a sinus infection and experienced inner-ear pain that can cause vestibular issues.“I was having balance (issues) and dizziness for six weeks and didn’t feel back to normal till May,” Haniger said. “I sprained my ankle in my first at-back back from the Covid IL because my equilibrium was still significantly affected. In my opinion, there’s no way I would’ve sprained my ankle if it wasn’t for Covid and the vestibular issues I got from Covid. I’ve never everted my ankle on a swing like that in my life.”
That ankle injury led to a twelve-week recovery that removed his statistics entirely from this study, yet his experience certainly seems relevant. After seeing a vestibular physical therapist, and rehabbing the ankle, Haniger finally feels 100 percent again.
Other players reported a two-week period in which they weren’t yet back to normal, even with the vaccine.
“I definitely felt tired, I felt tired going up and down the stairs,” said Giants outfielder Mike Yastrzemski of his experience. “That took about a week to get through. Tired, body aches. I felt it in the running, I felt it in my lungs for a bit, my lungs felt heavy. The more I ran and did physical activity, the quicker it went away and the better I felt. Two weeks in all.”
“The first week and a half coming back, I wasn’t all the way there,” said the A’s Chad Pinder about his post-Covid return. “Really tired, even going out to the field, I felt tired and heavy. Abnormally tired. That lasted about a week and a half.” Another player reported needing pre-game naps for a couple of weeks before he felt right.
In the most serious known case to date, pitcher Eduardo Rodriguez developed myocarditis as a result of infection with the virus and missed the 2020 season.
The anecdotal and statistical evidence agree that there is some post-return impact. The next question is to what degree these post-Covid impacts are caused by damage from Covid itself, or simply by the layoff and time away from exercise, preparation and maintenance while laid up with Covid.
“That gets slightly tricky when you layer in the fact that Covid is a cardiorespiratory thing that might be causing tissue damage there; that’s an extra layer of complication and complexity,” said Steffen Simmons, the director of high performance at Driveline Baseball.
It may seem unlikely that a professional athlete would lose fitness so quickly simply from a relatively brief layoff, but that is the reality of the highly specialized world of baseball, with its short bursts of energy use and peak activity. Simmons says that the work of Dr. Vladimir Issurin, scientific and professional coordinator of Elite Sport Department of the Israeli Olympic Committee at the Wingate Institute, has been important for how he (and many other trainers, including some with MLB teams) are considering the effort that needs to go into coming back from any time off due to injury.
“Generally what he’s found is that speed adaptations, so maximal sprint speed, will (decline) around five days plus or minus around three days depending on your training age and your training level,” Simmons said. “So, anywhere from two days to eight days, If you don’t do anything to get to maximal speed, you’re probably going to lose that, and maximal speed is obviously very important for baseball players.”
The creatine phosphate system is the primary system that baseball players use for game activity, as it controls movement in short, very high-intensity bursts. That also starts to fade in the same time frame. The aerobic system is a little more resilient, as an athlete will start to lose their adaptations there in 30 days, plus-or-minus five, according to Issurin’s work on the subject.
And all that applies just to a normal injury and layoff. Covid presents an additional set of unknowns, coupled with those respiratory issues we know by now to expect.
“People have inflammation in their lungs, even if they don’t recognize it,” said Dr. Preeti Malani, Professor of medicine and infectious disease physician at the University of Michigan. “Their energy level might not be as good as they return to the demands of professional athletics. Even young healthy people can be affected by this, and an elite athlete might notice this more because the performance level is different. If you’re just walking around at the grocery store, you might not notice the same things they will notice sprinting.”
The answer in baseball, as well as for anyone else, seems to be to go by feel, but also to create structures to help support those trying to come back from Covid.
“Teams need to have systems in place to give people room to adapt as they can,” said Dr. Malani. “Making room for people to recover properly is important. The fatigue is real, the respiratory capacity can be diminished, plus they’re sidelined. If you have Covid, I suspect you’re home and isolating and truly not doing anything, nothing vigorous, you’re not in the gym — at least you shouldn’t be.”
Clubs can’t just follow their standard return protocols with Covid-positive athletes, and must tailor their assessments and programs to what we know about how the virus operates if they want to get athletes back to 100 percent as quickly as possible.
“It’s tough to have one policy,” said one team exec, citing the variance in symptoms across cases.
“No two cases are the same,” agreed a major league coach, “but the hangover can last for weeks from a fatigue standpoint, and fatigue is the biggest predictor of injury.”
“Tough to navigate coming back from because you can feel still a little sick or not 100 percent normal, but anytime you’re sick through the season you just have to get through it,” said Haniger, who also noted that he doesn’t feel anyone was at fault for his possibly Covid-affected sprained ankle. “Unfortunately, Covid can have different effects than a normal cold.”
Most executives or coaches contacted for this piece didn’t know of a specific process for physically evaluating a player’s readiness to return from Covid. A couple mentioned that rehab stints were always an option, one that some players had taken to come back from particularly rough experiences with the virus. One team mentioned that they have different metrics-based hurdles players have to clear before they reach the field, based off of previous baselines for cardiac and aerobic fitness. That sounds like more of the ideal situation, according to Simmons.
“The first place to look is probably resting heart rate, respiratory rate, heart rate variability and see what kind of changes we can see,” said Simmons of an ideal process with an athlete. “If their changes are more oxidative in nature, we can get them doing aerobic work on a bike, a treadmill, running, whatever. If it’s more speed or power adaptation, say we tested them on the force plates … now we can attack that and get that peak power back up to where it was before, which is a much more simple task.”
For those concerned about some of the findings of cardiac problems related to getting the vaccine itself, Dr. Malani had a concise response that seems to be held up by the numbers presented by the Centers for Disease Control.
“Myocarditis from the vaccination is rare, but it happens,” she said. Still, “it’s much more likely to get heart effects from actual infection than from taking the vaccine.”
No matter what, teams need to be prepared to support players returning from Covid, as it’s still happening with regularity. Collecting biological information from their players voluntarily, so that they have baseline metrics for how their body works, may be a good starting point. Of course, not all players are rushing to give teams all of their biological data, because of privacy concerns, so teams don’t always have that on hand, especially for major league players. Planning to give players additional time to rid themselves of fatigue could make a difference, though that would be balanced against the desires of players and their coaches to get important performers back into action as quickly as possible. Thinking ahead about how it could impact big moments in the season could be important as well.
“In the postseason, if your star pitcher or closer gets Covid, you don’t have a deep bench in that spot,” pointed out Dr. Malani. “For planning purposes, that’s important; if I get Covid in September I may not be in good shape for the postseason.”
Overall, it seems the key for these athletes as they come back is in treating them individually.
“Consistent with a lot of the literature on Covid, we just don’t know everything yet. It seems to impact a ton of things and affect people in drastically different ways, that can be challenging,” said Simmons. “It really comes down to digging into that individual and how it’s affected them.”
And that’s an important sentiment for everyone, not just athletes.
Before the vaccine, things were worse — even for our sample, though impossibly small, the median ERA went up 35 points against pre-season projections post-Covid — but we have the methods now to lessen the impact.
“We have all these tools now for treating it,” said Lowrie. “We as a society have to realize that there is some risk in life, and we do the best we can to mitigate that risk. There was a point in time where we needed to be extremely careful, we didn’t know what it was, we didn’t know how to approach it. Now we have the tools that we are going to have. We can protect the vulnerable and also use those tools.”
But infection will still come, and some will have a harder time coming back than others.
“The more we can get people to come together, the better, at this point,” said Simmons. It holds true for an organization trying to support a returning athlete or for a network of family, friends, and doctors trying to support anyone coming back from Covid. It will be different for everyone.
(Top image: John Bradford / The Athletic; Photos: Rob Tingali / Sportschrome via Getty Images; Jordan Rowland / Unsplash)
