The Post Sports Live crew debates whether the Nationals should make a move to add a missing piece or stand pat before the July 31 trade deadline. (Post Sports Live/The Washington Post)

The Post Sports Live crew debates whether the Nationals should make a move to add a missing piece or stand pat before the July 31 trade deadline. (Post Sports Live/The Washington Post)

Ryan Zimmerman sat in the dirt just past first base at Coors Field, facing another potential crossroads in a season already marked by too many of them. Zimmerman had played through a degenerative shoulder, broken his thumb, changed positions and returned to the old position that tormented him. Now, in the sixth inning Tuesday night, he grabbed his right leg and waited for the trainer to reach him.

The Washington Nationals should have had so much to celebrate after their 7-4 victory over the Colorado Rockies. Adam LaRoche shattered a 4-4 tie in the seventh inning with a massive three-run homer off left-handed reliever Rex Brothers, his first since June 30. The Nationals moved two games ahead of the Atlanta Braves in the National League East, augmented the best record in the National League and won for the sixth time in seven games.

But they also confronted the possibility of losing the beating heart of their team for another extended stretch. Zimmerman exited in the sixth inning after he strained his right hamstring while running down the first base line. Zimmerman will receive an MRI exam Wednesday to determine the severity of his strain, Manager Matt Williams said. Zimmerman has already missed 44 games this season after he broke his right thumb, and given the ugly manner in which Zimmerman tumbled to the dirt, he may well be headed back to the disabled list.

“It’s concerning,” Williams said. “Any time you’ve got to leave the game with a hamstring injury, it’s concerning. We won’t know until we get a picture of it. We’ll do that in the morning.”

For 17 games, starting when Bryce Harper came off the disabled list June 30, the Nationals finally had the lineup they envisioned at their disposal. They went 12-5, scored 5.4 runs per game and gained two games on the Braves. Now the Nationals face the prospect of again trying to play with a lineup diminished by injury.

When the Nationals signed Jayson Werth for seven years and a $126 million in 2010, the move was largely criticized. The Post Sports Live crew reassesses the outfielder's huge contract and whether the move was worth it. (Post Sports Live/The Washington Post)

“You hate to see that happen, but that’s been the story of our season,” said Drew Storen, one of four relievers to throw a scoreless inning Tuesday night. “That’s what this game does to you. Every time you think [you] got it in gear, there’s no cruise control. You have to battle. We’ve done it all year. Fortunately, we’re so deep that we can step up. It’s tough to replace him. For however long it’s going to be, I think we’re going to be fine.”

While he beat out a 6-4-3 double play, Zimmerman’s right leg gave out as he neared first base. Zimmerman stepped on first base and stumbled, his right leg stiff, bearing no weight. He collapsed to the ground face first. Zimmerman quickly rolled over, sat up and summoned the dugout.

Williams and head athletic trainer Lee Kuntz jogged to first base. After a brief chat, Zimmerman hobbled off the field with his arm around Kuntz’s shoulder. He limped down the dugout steps with difficulty, unable to place any weight on his right leg.

The Nationals did not provide any information regarding Zimmerman’s injury prior to the end of the game. They could hope he suffered a mild muscle pull or a cramp, but his reaction suggested a worse fate.

“He’s swinging great, playing great,” Williams said. “But we’ll have to deal with it and see where we’re at tomorrow. Regardless, we still have to play.”

It has been a season of sacrifice for Zimmerman, who through various challenges has comported himself as an example for the rest of the clubhouse, professionalism embodied. He changed positions as he came off the disabled list, moving to left field after nine seasons spent as a pillar at third base. When Harper returned, Zimmerman moved back to third base, a position that tests his battered right shoulder. He risked embarrassment, without complaint, in multiple ways for the betterment of his team.

He also became a major cog in a lineup firing at full capacity, finally at full health. Since June 17, Zimmerman has hit .312 with a .376 on-base percentage and .505 slugging percentage. Tuesday afternoon, he joked with Ian Desmond about wearing an arm sleeve for the first time — “outfield swag,” Desmond called it. The Nationals this season are 33-19 with Zimmerman and 21-24 when he does not play.

“We’ll be fine,” LaRoche said. “If it happens to be a couple weeks, we’ll be alright. We hope it’s nothing more than that.”

Danny Espinosa replaced Zimmerman once he left Tuesday night. He played second, and Anthony Rendon moved to third to take over Zimmerman’s position. Utility infielder Zach Walters departed from Class AAA Syracuse late Tuesday night, according to a person familiar with the situation.

The Nationals had entered Tuesday night more concerned about the health of starter Jordan Zimmermann, who returned to the mound for the first time he suffered a right biceps strain July 11 in Philadelphia. Zimmermann scuttled any lingering worry over his arm in the first inning, when with two runners in scoring position and one out, he blew a 95-mph fastball past Carlos Gonzalez for strike three.

Zimmermann lacked crispness after the 10-day layoff, but he showed no ill effects from the strain. He allowed four runs on eight hits, two of them homers, in five innings. He walked none and struck out six. He threw only 76 pitches, many of them 95-mph fastballs, before his spot came up with the bases loaded and Nate McLouth pinch hit for him.

The Rockies surged ahead 3-0 when Nolan Arenado hammered a 95-mph fastball over the center field fence in the third for a two-run homer. Corey Dickerson made it 4-2 when he annihilated another fastball over the right field fence in the fifth.

“My command was way off, I’m hoping because of the layoff,” Zimmermann said. “I was just missing over the middle.”

The Nationals clawed back in the sixth. Rendon, who smacked three hits, and LaRoche knocked out starter Yohan Flande with singles. Rendon scored on Zimmerman’s fateful groundball. Espinosa pinch ran for Zimmerman, and he scored on Wilson Ramos’s infield single, which deflected off second baseman DJ LeMahieu’s glove.

The Nationals headed into the seventh inning tied. Denard Span greeted new reliever Brooks Brown with a walk, and Rendon followed with a single. After Brown struck out Jayson Werth, the Rockies summoned Brothers, their lone left-handed reliever, to face LaRoche. His approach?

“Try to make contact,” LaRoche said.

LaRoche, the Nationals’ best hitter through the season’s first three months, did not seem to be the likeliest hero. He had been hitting .130/.234/.167 in 64 plate appearances in July entering Tuesday. Williams planned to give him a day off Wednesday. He had not hit a homer off a lefty since May 28, 2013.

LaRoche took two balls, and Brothers fired a 93-mph fastball. LaRoche launched it into the visitors’ bullpen in right field, his 13th home run coming at just the right time.

“You swing hard enough times, you’re bound to run into something,” LaRoche said. “I’ve been playing long enough to know it takes one swing to get things turned around.”

With the Rockies’ lefty-heavy staff, LaRoche had faced many left-handed pitchers. Counter-intuitively, it may have helped him unlock his swing.

“It helps,” LaRoche said. “In general, it kind of forces you to stay back a little bit.”

LaRoche’s blast soothed the sting of possibly losing Zimmerman, but it could not take it away. The Nationals won again Tuesday night, but as they waited word on Zimmerman, they may have lost more than a game.