CHICAGO -- The Washington Nationals' offense came through for manager Davey Johnson on Wednesday night.
Washington had scored six runs over its past three games, but on Wednesday had its highest output since scoring 14 against the Mets on July 28.
Werth's three-run homer in the third inning off Jake Arrieta gave the Nationals a 6-1 lead and was his eighth since the All-Star break.
Hairston, who was traded by the Cubs on July 8, was pinch-hitting for Tanner Roark and hit his off James Russell (1-4) with two outs in the seventh to give the Nationals a 9-6 lead after they had given up a 6-1 lead.
That offense was a welcome sight for Johnson.
"Eleven runs, I think it's Christmas," Johnson said.
The 11 runs helped Washington overcome Anthony Rizzo's two homers and the Cubs' five-run fifth when they had seven hits to tie the game at 6.
Ross Ohlendorf was activated off the disabled list before Wednesday's game and allowed four runs and six hits and 4 1/3 innings.
Ohlendorf had been on the DL since Aug. 1 with right shoulder inflammation and was making only his third start of the season and didn't get through the fifth, getting replaced one batter after Rizzo's second homer cut the Washington lead to 6-3.
"Glad to get back out there. I felt good," Ohlendorf said. "Wish I had pitched deeper into the game for us but our offense did an awesome job."
Werth has been on a roll. He went 1 for 3 and has a .452 average in August, and has hit safely in 12 of his past 13 games.
The Nationals broke the game open on Werth's drive in the third, which came after Ryan Zimmerman singled and Bryce Harper walked. Werth hit a 3-0 pitch into the seats in left for his 18th homer of the season and a 6-1 lead.
Arrieta had been solid in two starts for the Cubs since coming from Baltimore on July 2 as part of the trade for Scott Feldman, allowing one earned run in 13 innings, but struggled Wednesday.
He went four innings and gave up six runs, including three in both the second and third innings.
"I didn't do my job tonight," Arrieta said. "I had enough weapons to pitch deep into the game and get our team a win, and I wasn't able to do that tonight."
The Cubs rallied in the fifth for five runs and seven hits, including six straight, to tie the game and chase Ohlendorf.
Rizzo hit a towering drive into the right-field bleachers for his second homer of the night, cutting the Washington lead to 6-3.
Starlin Castro reached on a fielder's choice before Rizzo's homer, which gave him his fourth multi-homer game of his career and the second of August, after hitting two against the Dodgers on Aug. 1.
Ohlendorf allowed Junior Lake to single and was replaced by Roark (3-0), who gave up run-scoring singles to Donnie Murphy and Cole Gillespie, before Welington Castillo's sacrifice fly to center tied the game.
Roark was charged with two runs in the fifth, but pitched 1 2/3 innings for the win.
"We out-hit them (14-11), but obviously two three-run homers, you ain't gonna win too many games with two three-run homers in one game," Cubs manager Dale Sveum said.
The second three-run homer didn't come until the seventh, and it came from somebody familiar to Sveum and the Cubs.
With two outs in the seventh, Hairston lined a 1-2 pitch into the seats for his three-run homer and ninth of the season.
Russell had gotten the first two outs of the inning before Harper doubled and Werth was intentionally walked.
Since coming to Washington, Hairston had struggled, hitting .200 with no home runs in 19 games.
For at least one at-bat, those struggles ended against his former team.
"It feels really good," Hairston said. "In that situation I wanted to capitalize. There's runners on and early in that at-bat my weight was shifting forward and I just wanted to make sure I stayed back and give myself the best opportunity to get a hit."
Washington SS Ian Desmond's back tightened up during batting practice, but he stayed in the game until the fifth when he was replaced by Anthony Rendon as part of a double switch. "He wasn't his usual self," Johnson said. ... Johnson said "there have been discussions" about giving INF Danny Espinosa a September call-up. Espinosa was sent to Triple-A Syracuse on a rehab assignment June 12 and optioned there on June 19 and is hitting .202 in 64 games. He hit .158 in 44 games for Washington. . To make room for Ohlendorf, the Nationals optioned LHP Ian Krol to Triple-A Syracuse. ... At 24, Rizzo became the second-youngest Cubs left-handed hitter to hit 20 home runs. Billy Williams has the mark, set in 1961. ... Thursday's pitching matchup is Washington's Stephen Strasburg (6-9, 2.93 ERA) against Chicago's Travis Wood (7-10, 3.13).