WASHINGTON -- They designated veteran catcher Miguel Montero for assignment Wednesday morning and then had third baseman Kris Bryant roll his ankle on the third-base bag that night during a loss.

The world champion Chicago Cubs then trailed 4-2 going into the top of the ninth Thursday, only to rally for three runs and beat the first-place Washington Nationals 5-4 to earn a split of the four-game series.

Tommy La Stella had a pinch-hit RBI single and Jon Jay had a two-run double to right-center with two outs in the ninth for the Cubs.

"It was no panic, it was no worry," La Stella said of the comeback. "We rallied behind each other. There was no panic when we got down. I think everyone in this clubhouse has the utmost confidence in one another."

"It was awesome. You never want to say you need a win because we certainly didn't," La Stella added. "It was definitely nice to get that one."

Wade Davis pitched the last of the ninth for his 16th save as he retired all three batters.

Blake Treinen (0-2), who gave up the three runs in the ninth, took the loss while Felix Pena (1-0), who pitched one scoreless inning, got the win.

The Nationals continue to be victimized by a poor bullpen, which produced two hitless innings before Treinen allowed three runs in the ninth.

Is Washington one reliever away from being a really good team?

"We are a really good team now," Washington manager Dusty Baker said. "We still need some help" in the bullpen.

Anthony Rendon hit a two-run, go-ahead homer in the seventh off Carl Edwards, Jr. to give the Nationals a 3-2 lead. Rendon hit a full-count pitch to left for his 16th homer of the year and 11th in his last 32 games.

Pinch-hitter Brian Goodwin of Washington had a bases-loaded single to drive in a run against reliever Pedro Strop to make it 4-2 later in the seventh.

Jeimer Candelario hit his first major league homer -- a solo shot to start the seventh -- to give the Cubs a 2-1 lead off starter Joe Ross. The homer came in his 42nd at-bat over the past two seasons.

"It worked out well," said Joe Maddon, the Cubs manager. "Tommy, great at-bat and Jon Jay, struggling all night, and then ball in the gap. There you have it."

Ross gave up two runs and five hits in 6 2/3 innings.

"It was tough today because Joe pitched a heck of a game. Our bullpen was spent today because we didn't have (Matt) Albers, we didn't have (Enny) Romero" since they pitched Wednesday, Baker said.

The Cubs took a 1-0 lead in the top of the first as Anthony Rizzo doubled with two outs and then scored on a single to left by Willson Contreras, who was thrown out trying for a double.

Washington tied the game in the bottom of the first. Bryce Harper walked with two outs and then scored on a double down the right field line by Ryan Zimmerman.

The double by Zimmerman tied the Montreal/Washington franchise record for doubles in a career at 360, also held by Tim Wallach. Zimmerman broke into the majors with Washington in 2005 and entered Thursday leading the league in slugging at .632.

Chicago starter Jon Lester gave up just three hits and one run in six innings with seven strikeouts.

"It was a bad series of events," Baker said of the loss.

NOTES: Cubs SS Addison Russell (shoulder) was back in the starting lineup for the first time since Sunday, when he left the game in Miami with a sore shoulder. He pinch-hit in the Monday and Tuesday games in Washington. ... 3B/OF Kris Bryant (ankle sprain) did not play Thursday . He left Wednesday's game in the fifth inning after stepping on the third-base bag after catching a foul pop. He could return Tuesday, according to manager Joe Maddon. ... Cubs OF Mike Zagunis, who made his major league debut June 22, was drafted out of Virginia Tech in 2014 by Chicago. He walked as a pinch-hitter in the seventh. ... Washington manager Dusty Baker was ejected for the first time as the Nationals manager, after arguing a strikeout by Ryan Raburn in the sixth. ... Washington SS Trea Turner left the game in the top of the ninth after he was hit by a pitch on the arm in the seventh. "It will probably be sore for a couple of days," Baker said. ... Washington is the only National League that has not been shutout.