Lackluster support has also hindered the right-hander in some recent matchups with the Philadelphia Phillies, and he won't have Bryce Harper's help in this one.
With Harper expected to rest an ailing hip, Zimmermann will try to remain among the league leaders by helping the Nationals top the Phillies and Roy Halladay on Wednesday night.
Zimmermann (15-8, 3.33 ERA) gave up three runs in 7 2-3 innings Friday against the New York Mets but was on the wrong end of a 3-2 result.
"Other than (a two-run homer to Ike Davis), I thought I pitched great," said Zimmermann, who was coming off a 7-2 win in Kansas City on Aug. 24.
That loss left him in a four-way tie for the NL wins lead and he'll be among three 15-game winners pitching Wednesday. Pittsburgh's Francisco Liriano and Colorado's Jorge De La Rosa are the other two with St. Louis' Adam Wainwright idle until Saturday.
Zimmermann will try to at least keep pace in that race by earning his second win in five career starts in Philadelphia. He gave up two runs over 6 1-3 innings in his most recent outing at Citizens Bank Park on July 11 but took the loss in a 3-1 defeat.
Zimmermann has a 2.89 ERA in his last six starts against the Phillies but only a 2-4 record. He's received one run or fewer in each of those losses.
Harper likely won't be available to help this time as he's slated to get the night off for the Nationals (70-68), who have an off day Thursday.
Harper has hit safely in 14 of his last 16 games but is 3 for 18 (.167) in his last five. He went 0 for 5 on Tuesday but scored two runs in a 9-6 victory over Philadelphia.
Wilson Ramos homered and drove in four runs as the Nationals remained 7 1/2 games behind Cincinnati for the NL's final wild-card berth.
They'll try to cut into that sizable deficit when they face Halladay (3-4, 7.94), who has experienced mixed results in his two starts since coming back from shoulder surgery.
The right-hander gave up two runs over six innings in his return, a 9-5 victory against Arizona on Aug. 25, but allowed five runs over five innings in humid conditions Friday at Wrigley Field. He avoided the loss when Philadelphia (63-76) rallied for a 6-5 victory.
"(Halladay) struggled a little bit on command," manager Ryne Sandberg told the team's website. "It was a little warm out there but he battled. He gave us some innings, and with our bullpen the way that it's been, we were able to keep the score in check and let the offense attempt to come back."
Halladay is 12-1 with a 2.42 ERA in his last 15 starts against the Nationals franchise with the most recent on Aug. 25, 2012.
Ramos is 4 for 9 against the two-time Cy Young Award winner, and Zimmermann is 2 for 3.
The Phillies are hoping Domonic Brown can return from an ailing Achilles as he's 4 for 6 with a double all-time against Zimmermann.