Jon Lester needed just nine pitches to retire the first two White Sox batters he faced Monday night. He got Alejandro De Aza to pop out to shortstop Stephen Drew and struck out Alexei Ramirez swinging on a changeup, the pitch that has served Lester so well this season.

It appeared the left-hander was picking up where he had left off in recent outings. In his previous three starts, Lester had gone 2-0 with a 2.05 ERA, giving up five runs over 22 innings.

Instead, the game began to quickly unravel for Lester after that.

He gave up a single to Alex Rios, the next batter, before walking Paul Konerko, bringing up Adam Dunn, who was hitting just .169. But in previous six games Dunn was hitting .364, going 8-for-22, with four home runs.

Dunn added to that total, with a blast to right field for his 11th home run of the season.

The White Sox added to their run total in the second when No. 9 hitter Tyler Greene, De Aza, and Ramirez connected for three straight doubles, scoring two runs.

Chicago added a run in the fifth. Ramirez led off by reaching on Will Middlebrooks’ error, and Rios walked before being erased when Konerko grounded into a double play. After a walk to Dunn, Dayan Viciedo’s single scored Ramirez for an unearned run.

Lester took his first loss of the season, falling to 6-1 in 10 starts, as the Red Sox fell to the White Sox, 6-4. He went six innings, giving up seven hits, matching season highs with six runs and five earned runs, along with three walks, two strikeouts, and a home run. He threw 109 pitches, 70 strikes, as his ERA rose from 2.72 to 3.15. All the runs he allowed came with two outs.