The plan when Ryan Zimmerman returned from the injured list in September was simple. Manager Dave Martinez would ease the first baseman back into the Washington Nationals lineup, mostly against left-handed starters. He could pinch-hit, too. But in the last few days, without warning, Zimmerman has become something he hadn’t been all season: The Nationals’ every day first baseman.

The most notable part of Zimmerman starting every night is that, as of Saturday, he’d done so against three straight right-handed starters. The National League Championship Series was supposed to present a challenge to Martinez because the St. Louis Cardinals don’t have a left-handed starter. This could have forced the manager’s hand because, despite Zimmerman’s hot bat, his career-long splits — crushing southpaws, struggling against right-handers — have only sharpened in the last few years. This season, his on-base-plus-slugging-percentage against lefties is elite (.966) while his OBP against righties is abysmal (.645).

It would have made sense if Martinez shuffled his lineup against the Cardinals by benching Zimmerman, shifting second baseman Howie Kendrick to first and starting switch-hitter Asdrúbal Cabrera at second. He’d done that for the last month, including during the wild-card game and early in the NL Division Series. But he didn’t; Zimmerman last sat in Game 3 against the Los Angeles Dodgers. He started the next night against left-handed starter Rich Hill, but he delivered the game’s most important hit, a three-run home run in the fifth inning, off right-hander Pedro Baez. His indiscriminate mashing this postseason — 7 for 23 with two doubles and the homer — has prevented Martinez from taking him out.

“He's swinging the bat well,” Martinez said, explaining why he keeps penciling in Zimmerman. “I like him in the lineup.”

The manager also pointed out Zimmerman is running well after he missed much of the season because of plantar fasciitis in his right foot, and he remains their best defensive option at first base. Zimmerman highlighted this fact with his diving grab on a line drive during Game 1 against the Cardinals which, at the time, kept intact Aníbal Sánchez’s no-hitter. Zimmerman joked he only made the play because his 35-year-old body has entered “the playoff time machine,” and teammates teased him he might need to take a few days off.

Yet, in a way, that situation embodied what the playoffs do for the Nationals, the team with baseball’s oldest average age by more than a year (31.1). He and Kendrick, the pair emerging as the right side of the infield, are older veterans who couldn’t play every day this season even if they wanted to. But now the postseason schedule affords an off day every two or three games, providing ample recovery time and transforming them once again into everyday starters.

Fans criticized Martinez this season for not regularly starting Kendrick, and Zimmerman noticed. The argument made sense on its face: The 36-year-old looked fully healed from the ruptured Achilles’ which ended his season early the year before, and his .966 OPS was 10th in MLB this season among hitters with 370 or more plate appearances. But Zimmerman thought it missed the point.

“The reason why he's doing that is because he gets the off days,” Zimmerman said, speaking for more than just Kendrick. “People don't quite understand that.”

This resurgence at the plate, Zimmerman noted, can be attributed to the lengthy rehab the Nationals afforded him. The team was managing without him in August using a rotation of Brian Dozier, Matt Adams, Cabrera and Kendrick on the right side of the infield, so they gave him eight games with Class AA Harrisburg. He worked another 53 at-bats in the big leagues in September and, the later the season got, the more comfortable he felt.

“[Those six weeks] really kind of helped me settle in,” Zimmerman said. “Now, I've had some at-bats and feel pretty good up there.”

His return has redefined the Nationals’ depth, an area which players themselves saw as a strength throughout the year. Martinez needed to keep Kendrick’s bat in the lineup and ride the hot hand with Zimmerman, so the players who usually might rotate in at times, like Cabrera, are relegated to pinch-hit roles. Same goes for Dozier and Adams, whose scorching first few months of the season had many clamoring to end the timeshare with Zimmerman and install Adams as the everyday first baseman.

Adams had 20 home runs and a solid .831 OPS by mid-August, but he sustained a sprained AC joint in his left shoulder and slumped for the last six weeks, never hitting another home run as his OPS dropped nearly 100 points. It’s unclear if Adams has fully healed from the shoulder injury, and he’s appeared in only three games this postseason, all pinch-hit opportunities. His single in Game 2 against the Cardinals, though, set up a two-run double from Adam Eaton which ultimately became the difference in the win.

This situation, Zimmerman picking up the team, doesn’t surprise Eaton because he believes this is what the team has done all year long. Depth is why they have withstood injuries and slumps and their poor start to this season. No one illustrates that better than Zimmerman.

“All you guys think he’s old and he’s done,” Eaton said, speaking for more than Zimmerman. “But I think he’s going to write a different script.”

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