WASHINGTON -- There haven’t been many starting pitchers more effective when healthy this season than Reynaldo López, and few teams have relied more on their rotation during the stretch run than the Braves. Now, Atlanta may find itself fighting for its seventh straight postseason appearance without López and his 2.03 ERA.

López’s status is uncertain after he left Tuesday’s start after just one inning with right shoulder tightness, though Atlanta’s offense responded with its best showing in more than three weeks to lead the Braves to a 12-0 win at Nationals Park. Michael Harris II, Orlando Arcia and Sean Murphy all homered (Harris hit a pair), while Ramón Laureano drove in three runs in support of what turned into a bullpen game after López’s early exit.

The victory moved Atlanta into a tie for the National League’s final Wild Card spot with the Mets, who lost to Toronto, with 17 games to play. The Braves said López would undergo an MRI on Wednesday to gauge the severity of the issue.

“We’ll determine something tomorrow,” manager Brian Snitker said. “He’s checking out OK. I saw the velocities were not good, and I talked to him after and made him fess up.”

López’s velocity was noticeably down during his lone inning of work; his fastball averaged 91.9 mph -- 3.6 mph lower than his season average -- per Statcast. His curveball, changeup and slider all registered averages between 2.3 and 4.7 mph lower than his season averages, as well.

“I didn’t really know what was happening ,” López said through team interpreter Franco García. “The first pitch went out, and I thought it was 95, and I look up and it was 89. That took me by surprise. That’s something I wasn’t expecting. I was definitely relieved when everything came back normal and good, and right now I think we’re just being overly cautious.”

“He wanted to keep going,” said Snitker. “But when he stepped on it, he didn’t feel great. It’s something. But we’ll know more when they get him looked at a little more.”

A converted reliever, López worked out of the bullpen in 2022 and ‘23 (and spent considerable time in the ‘pen in ‘21 as well) prior to the Braves signing him to a three-year deal last winter with the idea of inserting him into their rotation. They’ve been intentional about managing López’s workload throughout the year, building in extra rest with an eye toward decreasing the risk of injury to a pitcher who, entering the 2024 season, had not eclipsed 66 innings in a season since 2019.

The experiment worked wonderfully. López thrived back in the rotation. His 2.03 ERA through 24 starts leads all MLB starters (min. 100 IP), and before Tuesday’s one-inning start, he’d averaged 5.5 innings across 23 starts. He missed two weeks in August with right forearm inflammation, but has otherwise been healthy, and had been pitching extremely well since returning from the IL, recording a 1.96 ERA and 34 strikeouts across his past four starts.

“We didn’t know, going into this, what we would get,” Snitker said of the López signing Tuesday afternoon. “But it’s been great. He’s been awesome every time out. The ability to limit damage when he gets guys on has been unbelievable. It’s been a lot of fun watching him go.”

At this point in the season, losing López for any time at all would be impactful for a Braves team clawing for a playoff spot. Their offense has struggled of late without mainstays Ronald Acuña Jr., Austin Riley and Ozzie Albies, all of whom have missed significant time to injury. They’ve relied heavily on their rotation in the interim with great success, as Atlanta's starters pitched to a 2.36 ERA over the past 28 games entering Tuesday, though the Braves went just 17-11 in those games with the offense scuffling.

The Braves entered Tuesday ranked 28th in the league in runs per game in September with 2.9, and had hit just three homers this month. They hit four against the Nats as part of a 15-hit barrage and tied their second-highest run total of the year. The 15 hits were also their most in a game since April 6.

“We know what’s at stake here, this time of year” said Jesse Chavez, who threw three scoreless innings in relief of López. “To be able to come in and pick up [López] ... we get to watch a show every time he goes out there, which is pretty nice. You know that. This was the one day we had to pick him up, for something we really hope isn’t serious.”