The right-hander will take the hill in Sunday night's series finale on ESPN against visiting Philadelphia, hoping to get a little run support and lead the Nats to a series sweep along the way.
Philadelphia has split its last six games. The Nationals, who entered play on Saturday with the third-fewest runs scored this season, are in first place in the competitive National League East despite that fact.
Zimmermann boasts a 1.89 ERA this year, but has just one victory in five starts. He has allowed more than one earned run in just one game this year (his most recent outing, when he surrendered three against the D-backs), but the Nationals have averaged just 3.2 runs per game in contests Zimmermann has started.
"I really don't think of that when I'm out there," Zimmermann said when asked if he feels he needs to be perfect every time he takes the mound. "I just think about pitching my game and going as deep in the ballgame as I can. Whatever the outcome may be, it's what it's going to be. I can't really speak for the offense. I just have to go out and pitch the way I can pitch."
The Phillies will counter Sunday with lefty Cole Hamels, who surrendered six hits, two runs and two walks while striking out six in his last start, against the Braves on Tuesday.
"From a pitching standpoint, we just have to minimize the damage," Hamels said after that outing. "I know we have great pitchers, but we can't take anything for granted. We have to keep plugging away. I still think we have a lot of work to do."
Phillies: Struggling against Washington
Philadelphia was out-hit, 15-5, by the Nationals on Saturday and has now lost seven in a row to its NL East rivals for the first time since 1989, when the Washington franchise was in Montreal. Washington is 5 1/2 games ahead of the Phillies in the division standings.
Chase Utley was back with the Phillies in Washington on Saturday, though he remains at least a few weeks away from rejoining the Philadelphia lineup.
Cliff Lee threw a successful bullpen session Saturday morning and says he will be ready to start on Wednesday against the Mets.
Nationals: Fine quality pitching
Washington's starting pitchers have thrown 12 quality starts in 13 games dating back to April 20. The rotation's collective ERA in that span is 2.10 (19 earned runs in 81 1/3 innings).
The Nationals have won 12 consecutive one-run games at Nationals Park, dating back to Aug. 21, 2011. Eight of those victories have come this year.
The Phillies are 4-6 in day games this year, though the club's pitchers have posted a 3.14 ERA (31 earned runs in 88 2/3 innings) in those contests.
Nationals pitchers have allowed just nine homers this year, good for the fewest in the Majors. The second-closest teams -- the Giants and Marlins -- entered Saturday with 17 apiece.