The game was tied at 1 when the Nationals took the lead in the eighth. Denard Span led off with a double. The Cubs challenged the call on the field, believing that Span was tagged out by shortstop Starlin Castro, but the replay showed that Span was safe.
"I knew it was a close play. I didn't feel him tag me, but everything happened so fast," Span said.
Anthony Rendon, who would learn he was an NL Final Vote candidate following the game, then flied out to deep right field, but Span was unable to tag up on the play.
"We didn't execute very well today," Williams said. "Against a guy like [reliever Pedro Strop], we have to make sure we do that."
Fortunately for the Nats, Zimmerman came to the plate and singled to left field off Strop, scoring Span.
"A slider was what I hit," Zimmerman said. "The back of their bullpen, they have some really good arms. ... That was a game that we needed to win."
Tyler Clippard picked up the victory, while Rafael Soriano notched his 21st save of the season.
NL All-Star Jordan Zimmermann started the game for Washington and was solid, pitching six shutout innings, allowing seven hits and striking out five batters. He did well despite not having his fastball command.
"The whole game I fell behind hitters early. I wasn't able to throw first-pitch strikes. I was able to get out of a few jams. Other than that, I threw the ball well," said Zimmermann.
Zimmermann was given a 1-0 lead in the first inning off Cubs right-hander Jake Arrieta. Span led off with a double, advanced to third on a groundout by Rendon and scored on a groundout by Jayson Werth.
Arrieta was just as tough as Zimmermann. He pitched six innings, allowed the one run on four hits and struck out five. The Nationals had another opportunity to score in the fifth. Ian Desmond and Wilson Ramos opened the inning with singles, but Arrieta retired the next three hitters -- Zimmermann, Span and Rendon -- in order.
"They've got a really good ballclub," Arrieta said. "Atlanta won nine in a row before losing. Without that, those guys are in first place, so a very high quality ball club. Top to bottom, their order is very strong.
"I was looking up in one of the innings and I saw Desmond and Ramos hitting seventh and eighth. And I said, 'Wow, these guys are pretty good.' So it was a dogfight, though. I really had to grind it out there. I had guys on base, had to make pitches in big situations and I was able to do that. Had a couple walks that were uncharacteristic. But it was good. [It kept] us in the game."
The Cubs tied the game in the top of the seventh inning off reliever Drew Storen. With the bases loaded and one out, Castro hit a sacrifice fly to score Chris Coghlan.
Clippard entered the game in the eighth and also found himself in trouble. The Cubs had runners on second and third with one out, but Clippard managed to get out of the inning. Welington Castillo struck out looking on a splitter and Ryan Sweeney grounded out to Rendon at second to end the inning.
"I'm looking for a ground ball or a popup in the infield. Fortunately in that situation, Castillo took it for a strike, so it worked out," Clippard said.