Zimmermann will attempt to collect his 18th victory and help Washington's rebound from the end to a season-high win streak in Sunday's series finale against the Philadelphia Phillies.
The Nationals (78-70) pulled within 4 1/2 games of Cincinnati for the NL's final wild card berth on Friday after their seventh straight win but couldn't keep that run going Saturday. Washington's rally from a four-run deficit came up short in a 5-4 defeat to Philadelphia.
The loss also ended a five-game home win streak against the Phillies and was the second in the last eight overall meetings.
"We're still fine. We've just got to win the games," manager Davey Johnson said. "Just got to keep winning."
The Nationals are now 5 1/2 games back of the Reds with 14 to play, and Zimmermann (17-8, 3.36 ERA) will try to help cut that deficit while earning a third straight win. He recorded the first of his back-to-back victories Sept. 4 against Philadelphia (69-79).
Zimmermann gave up two runs over seven innings in that game and improved to 2-1 with a 2.66 ERA in three matchups this season. He allowed three runs over five innings Tuesday in a 6-3 victory over the New York Mets despite admittedly not having his best command.
"As long as the team wins, I don't care how many wins I have," he said. "We want to finish strong. We want to show everyone that we're not going to roll over and quit. We're going to fight until the end. We've got a veteran club that gives 100 percent every day. We're going to take it one game at a time and see what happens."
Denard Span will try to aid the right-hander while extending his career-best 25-game hit streak, which is also the second-longest in the majors this season. Colorado's Michael Cuddyer had a 27-gamer from May 28-June 30.
Span, batting .387 during his streak, is 12 for 29 (.414) in his last seven games against Philadelphia but has never faced Tyler Cloyd (2-4, 4.56).
The Phillies right-hander was tagged for seven runs and nine hits over four innings in his return to the majors Tuesday, an 8-2 loss to San Diego. Cloyd is 0-2 with a 10.80 ERA in his last two starts.
"I was leaving pitches up and made a lot of mistakes," Cloyd said. "My pitches were getting a lot of the plate. ... I got off the game plan and didn't throw enough off-speed pitches."
Cloyd also struggled in his only start against Washington on Sept. 27. He gave up six runs and six hits, including three homers, in a 7-3 loss.
Bryce Harper went 2 for 3 with a solo home run against the right-hander in that game.
Philadelphia's Carlos Ruiz, 10 for 20 with 10 RBIs in his last five games, is 1 for 5 versus Zimmermann this season.