Mookie Betts, Stephen Strasburg, and 2021’s Most Irreplaceable Players

Which players are most essential to their team’s postseason odds? While that list contains many of the best players in baseball, it’s not a strict ranking of the sport’s brightest stars. When looking at who is the most irreplaceable in the short-term, there are questions beyond just how good the player in question is. It becomes a matter of marginal utility. To a team already saddled with a doomed 2021 outlook, losing a star is unfortunate — obviously very much so for the player in question — but won’t really affect their chances of making the playoffs. The Colorado Rockies could build a time machine, kidnap Ted Williams, and stick a very confused Splendid Splinter in their lineup and it still wouldn’t change their near-term fate. And the same goes for teams at the opposite end of the spectrum — you can’t tip over your house with a leaf blower.

Of course, some teams are simply better equipped to deal with these kinds of nasty surprises than others, able to rely on enviable depth to weather absences. Two such nasty surprises have happened recently and illustrate the point well, albeit in opposite directions. Stephen Strasburg of the Washington Nationals was placed on the Injured List with shoulder inflammation after a mess of a start that saw him caught rubbing his shoulder on camera. (For more on the Strasburg injury, check out my colleague Jay Jaffe’s piece discussing what it means to Washington.) Another scare involved Mookie Betts, who took a hard, high-and-in offering from Rafael Montero directly on his forearm.

Luckily, Betts’ injury seems unlikely to sideline his for long — Dave Roberts says he expects him back later this week — but even if it had meant a longer absence, the Dodgers would have had little need to panic. Even in the worst-case scenario, where the team loses him for the rest of the season, it’s hard to derail this playoff train; the ZiPS projections have their playoff probability collapsing from 99.6% to…97.5%. A drop-off of two percentage points is a relatively minor one, smaller than the projection change if the White Sox lost Adam Eaton or the Astros had to suddenly replace Yuli Gurriel. Presumably, we have unanimous agreement that Betts is easily the most valuable player listed here.

The Nationals, on the other hand, are very reliant on their stars. Should they lose any of their key players — mainly Strasburg, Juan Soto, Trea Turner, Max Scherzer — it would nearly doom their October hopes. Soto joined Strasberg on the IL yesterday after suffering a strained left shoulder. Losing him for the duration would cause the club to miss the playoffs in 81% of the simulations in which the Nats would otherwise make it.

As steep as that sounds, from a quantitative standpoint, losing Soto isn’t the biggest possible loss in baseball in terms of playoff probability; ZiPS already sees the Nats having an uphill climb at 12.2%. The teams that have the most to lose are those with two key elements: a playoff fate that is very much undecided and and a lack of ready replacements elsewhere in the organization. So, as of Tuesday morning, here are baseball’s most irreplaceable players. The below changes in playoff odds assume a season-ending injury and the use of an in-house replacement. Just to illustrate how changeable this list is, only two of the top 10 are repeats from 2020.

Mike Trout, Los Angeles Angels (-35.5%)

As the best player of his generation, Trout has a way of finishing at the top of lists, but his placement here is actually fairly unusual. He has sometimes missed this ranking completely, as the Angels have an impeccable record of building inadequate teams around their franchise player. But the AL West is open enough, and the Angels are good enough, that this is the year they really can’t afford to lose him. Trout going down would already be a huge loss even if the Angels had an extra league-average outfielder hanging around the roster. But with the likely in-house solution being to shuffle around the outfield, resulting in more playing for Juan Lagares and some combination of Scott Schebler and eventually Taylor Ward, that’s not the team’s situation.

Gerrit Cole, New York Yankees (-29.5%)

That Cole ranks so highly is not a slight on the quality of the Yankees’ starting pitching. They’re actually quite deep with interesting, talented arms who could step in if the worst should happen and they lose their ace. What is a problem is that after Cole, the Yankees have a lot of pitchers with spotty injury records. ZiPS already assumes that the team will have to turn to that depth multiple times before 2021’s final pitch is thrown. To lose the guy they want to set-and-forget at 200 innings would be a big blow. Complicating the picture is that while the Yankees are still the favorite, their slow start does matter and means that they’ve already lost a good chunk of their margin for error over the Rays, Blue Jays, and Red Sox in the division.

Ronald Acuña Jr., Atlanta Braves (-28.3%)

Acuña wasn’t the National League MVP in 2020, but he’s certainly the player I’d least like to lose if I owned the Atlanta Braves. All the projection systems love him for obvious reasons, but none more than ZiPS, which sees him as the only player in baseball to have non-laughable odds of becoming baseball’s first 50/50 club member. Drew Waters, Ender Inciarte, and Guillermo Heredia could replace the at-bats, but none of them have the recipe to replace the awesomesauce Acuña uses to feast on opposing pitchers.

Alex Bregman, Houston Astros (-28.1%)

Houston’s rotation depth over the last four years has descended from utopia to yikes and now the team’s offense is absolutely crucial to the Astros playing October baseball. The franchise’s offensive core may have originally been led by Jose Altuve and then Carlos Correa and George Springer, but Alex Bregman is now The Man, the hitter they can least afford to have missing from the lineup. ZiPS sees Aledmys Díaz and Abraham Toro as better-than-replacement talent, but Houston’s unlikely to run away with the division the way it has in some recent seasons, making every win crucial.

Jacob deGrom, New York Mets (-25.0%)

deGrom drops from first to fourth on the list, but that’s not due to any decline in his performance. Rather, with the Mets under new ownership, the team didn’t go into the season with five starting pitchers who looked good on paper and a roster that couldn’t withstand injuries to the rotation. This time around, the Mets actually have options. None of them could fully replace deGrom, mind you, but plenty could at least be respectable fifth starters on a good team.

Carlos Correa, Houston Astros (-24.1%)

Given Correa’s injury history, the fact that he ranks highly on a list like this should greatly concern the Astros. ZiPS sees Bregman as the clearly superior player but also sees the options after Correa as less enticing. Díaz isn’t a particularly good defensive shortstop, and Toro wouldn’t be an option at the position. Alex De Goti has interesting power but is a massive downgrade from Correa. Houston would likely have to explore a trade if misfortune befell Correa, but the team may have other needs, so that’s not a great scenario either.

Luis Robert, Chicago White Sox (-23.2%)

From a straight-up projection standpoint, Robert falls short of most of the names on this list. Just on the Sox, ZiPS thinks Lucas Giolito is a significantly more valuable player overall, at least when he’s not pitching in the morning. But if something should happen to Giolito, Chicago has spare arms to patch up the hole. If the team loses Robert, let’s just say ZiPS does not have a case of Leurymania or Engelalia. The race with the Twins is likely going to be a tight one and the Royals have shown surprising spunk. The White Sox could ill afford an injury to their center fielder.

Byron Buxton, Minnesota Twins (-22.7%)

Is this the year that Byron Buxton finally stays healthy and is awesome? In just nine games, he’s already collected an impressive 1.5 WAR! Buxton will fall off from his 15-WAR pace, of course, but a lot of the scenarios in which ZiPS sees Minnesota taking down Chicago involve a solid season from Buxton. Even if his offense regressed hard toward his career 93 wRC+, the team would struggle to replace his glove, which has remained a major plus even through his various injuries.

Anthony Rendon, Los Angeles Angels (-21.8%)

To nobody’s surprise, Rendon isn’t quite the player that Mike Trout is. But the Angels have real playoff hopes, and even with the team having better replacements for injured infielders than outfielders, it would struggle to replace Rendon. Franklin Barreto’s elbow is enough to just squeeze Rendon onto this list, where he’d otherwise finish 12th, with Gleyber Torres taking the 10-spot.

Freddie Freeman, Atlanta Braves (-21.7%)

I love Pablo Sandoval, but not as my starting first baseman. Nor would Austin Riley playing first (with Johan Camargo, Orlando Arcia, and Ehire Adrianza pitching in at third) remedy the situation. Freeman’s the best first baseman in baseball, and even if the position isn’t as important as it was 40 years ago, he’s a crucial part of the lineup.