ATLANTA — Washington Nationals first baseman Ryan Zimmerman exited Sunday’s game against the Atlanta Braves in the second inning after grimacing halfway up the first base line at SunTrust Park. He felt pain in his right heel, related to the plantar fasciitis in his right foot that forced him to miss two months this season. Zimmerman will undergo an MRI exam Monday, once the team is back in Washington, and the Nationals will then decide whether the 34-year-old needs to go back to the injured list.

“I’ve actually been feeling really good,” Zimmerman said after Washington’s 7-1 loss to the Braves. "The last three or four days or so have been the best it’s felt and kind of started to — not turn a corner where it’s completely gone — but definitely feel like I can be a little bit more athletic and do some things.

"But, yeah, it’s frustrating. I’ve been feeling better at the plate and been starting to get back into it a little bit, and then for it to act up again, we’ll see what it says tomorrow and go from there.”

Zimmerman’s lengthy injury history makes this latest development all the more concerning. His improvement since returning in late June — with 13 hits, including five doubles, in 46 plate appearances — has helped boost a surging team. The veteran has had trouble staying healthy in the back half of his career, playing in just 85 games last season, which is why Manager Dave Martinez has been careful with his playing time.

But Zimmerman was in the lineup Sunday, and has been often in favor of Matt Adams, because his foot was beginning to feel back to normal. Now another setback could dash any progress.

Zimmerman had ripped a line drive at third baseman Josh Donaldson, jogged out of the box, then sped up once he saw Donaldson dive for the ball. Yet it had trickled away from Donaldson, and Zimmerman could have reached without shifting into another gear.

“It’s been really frustrating,” Zimmerman said at his locker, carefully pulling a shoe over the blue wrap on his right foot. It sounded like many of the interviews he has done this season, in which nagging injuries have overshadowed anything he has done on the field.

If Zimmerman is sidelined and makes another trip to the injured list, the Nationals still have considerable depth at first base. Earlier this season, Adams and Howie Kendrick formed a solid lefty-righty platoon in Zimmerman’s absence. Since Zimmerman returned, Martinez has faced a daily puzzle of how to fit him, Adams, Kendrick and second baseman Brian Dozier into two lineup spots. But Adams and Kendrick aside, losing Zimmerman would thin what has become a deep bench in recent weeks.

The Nationals are carrying four reserves — Adams, Kendrick, Gerardo Parra and a second catcher — and potential options to replace Zimmerman are scarce. Utility infielder Adrián Sanchez is with Class AA Harrisburg. So are outfielder Michael A. Taylor and catcher Spencer Kieboom. Then they have infielder Jake Noll, shortstop Carter Kieboom and utility man Wilmer Difo with Class AAA Fresno. Washington will hope for good news on Zimmerman and that it doesn’t need to choose from that lot quite yet.

“He’s been fine,” Martinez said Sunday night. “He’s been taking care of it, doing all these treatments and that type of stuff. He hit the ball, he thought Donaldson had caught it and ran hard to first base, so we’ll see what happens after the MRI tomorrow.”

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