Now it's Bryce Harper's knee -- the left one. This is one part of the team's anatomy that must be relatively healthy in order for the Nationals to take flight as anticipated with their star-studded cast.
Harper was a scratch on Tuesday night against Zack Greinke after banging the knee against the Dodger Stadium turf in Monday night's series opener, taken 8-3 by the Nationals with the kind of power display their fans have been waiting to celebrate.
Playing with customary aggression, Harper landed hard in the third inning on what became Jose Peraza's first Major League hit, a triple, as the Dodgers' temporary second baseman with Howie Kendrick shelved by a hamstring ailment. A charging Harper couldn't make the catch, but he stayed in the game and made a laser throw and sprawling stab, showcasing the Gold Glove-caliber abilities that complete his total game.
"Overnight, there was pretty significant swelling," Nationals manager Matt Williams said. "He's walking fine but has limited mobility. We'll see how it is [on Wednesday]. On occasion he bangs that knee. He doesn't have a problem structurally, so it's day-to-day."
If Harper can't make it in the finale of the series on Wednesday, fans will be deprived of one of the most thrilling confrontations in the sport: Clayton Kershaw, the winner of the 2014 NL MVP Award, vs. Harper, the early favorite to succeed him.
Harper plays with a fierce intensity, but he speaks softly and politely one-on-one, sprinkling sentences with "sir." There seems to be a calmly planned, specific purpose to everything the Nationals' young superstar does.
An independent thinker, he said he generally refrains from taking batting practice against right-handed pitching. Really, what's the point? He's crushing righties to the tune of .336/.466/.680 this season, with 24 of his 29 home runs. Why mess with success?
"Taking BP off a lefty helps me keep my front side in," Harper said. "Lefties get you where you want to be."
Lefties frequently get left-handed hitters, even really good ones, tied to the bench in a platoon. This thinking doesn't apply as often to right-handed hitters facing righties, largely because there are so many more of those on both sides of the equation.
Harper is a rare exception to this and many other traditional theories.
One of the most remarkable aspects of his brilliant 2015 season is that he has clubbed lefties almost as thoroughly as righties with a .327/.444/.582 slash line.
"I've been healthy," Harper said on Monday night when asked for an explanation. "I haven't taken a month and a half, two months off. Staying healthy and strong, that's the key for me."
With all the injured parties around him, Harper has been more valuable to his team than any player in the league. He's the NL's answer to the Angels' Mike Trout, his former Arizona Fall League teammate.
Harper's success from the left side against lefties underscores his growth as a hitter at 22 in his fourth season.
"I never had a problem with lefties growing up," Harper said. "I raked against them in college, around .350."
Harper rarely gets cheated, but manages to make fairly consistent contact for a power hitter. He has almost as many walks (82) as strikeouts (90).
Kershaw has had the upper hand in their three meetings. Harper is 1-for-9 with six strikeouts, but that one hit was a home run. He unloaded to right center on a first-pitch fastball at Dodger Stadium last Sept. 2 in the seventh inning. It was the only blemish in Kershaw's 4-1 victory.
On July 18 in D.C., in the first series after the All-Star break, Kershaw dominated the Nationals with 14 strikeouts in eight shutout innings. Harper was victimized three times.
When Kenley Jansen replaced the ace in the ninth, Harper slammed a two-run homer for the only runs in his team's 4-2 loss.
The return of Zimmerman and Werth, the right-handed boppers, should enable Harper, the team's No. 3 hitter, to see more pitches in his happy zone.
Since coming off the disabled list on July 28 along with Werth, Zimmerman has been on fire: seven doubles, four homers and 11 RBIs in 14 games, batting .333.
"It's great having those guys back in the lineup behind me," Harper said. "It helps everybody, not just me."
If Harper's absence is brief and the varsity is back in business, it's bad news for the front-running Mets and the rest of the NL East.
"I think we're getting there," Zimmerman said. "It'll be nice to get everyone back. It's that time of the year."
Lyle Spencer is a national reporter and columnist for MLB.com. Follow him on Twitter @LyleMSpencer. This story was not subject to the approval of Major League Baseball or its clubs.