Jon Lester had a 6.51 ERA in his first eight starts.
Lester has a 2.40 ERA in his last eight starts. He had a 0.00 ERA on Monday in Baltimore.
"Earlier, he's still getting his feet on the ground, getting his feel," catcher Jason Varitek said. "Everybody forgets that he's still 25. He's still developing. He still may go into ruts and do things, but that's part of his maturity."
Opponents hit .311 off Lester through May 15.
Opponents have hit .211 off Lester since May 21. The Orioles went 5-for-26 (.193) against him on Monday in Baltimore.
"It took him a while to get into that feeling," manager Terry Francona said. "But, boy, when things are going a little rocky, he and John Farrell go out there and put their heads together and keep working, and, boy, we're seeing those results now."
Lester allowed 10 home runs in his first eight starts.
Lester has allowed three home runs in his last eight starts. He allowed no home runs on Monday in Baltimore.
"When he was coming up and learning how to pitch, you could see his breaking ball and how he'd get it over for strikes," manager Terry Francona said. "Now he's starting to get some down-and-in to those righties and getting some action. That was a pretty explosive breaking ball."
Lester struck out 54 and walked 16 in his first 47 innings.
Lester has struck out 60 and walked 14 in his last 52 1/3 innings. He struck out eight and walked no one on Monday in Baltimore.
"I don't think he's lacked confidence," Varitek said. "When you're learning and learning yourself at the big-league level, you'll have bumps. But he's had more good stuff happen to him than bumps."
The Red Sox now are 18 games above .500 and have a .618 winning percentage and have a 3 1/2-game lead on the New York Yankees. They're 17-8 in the month of June.
Imagine what they'll do when they start to click.
From April 6-May 15, Red Sox hitters hit .277 with an OPS of .814.
From April 6-May 15, Red Sox pitchers had a 4.90 ERA.
Since May 16, Red Sox hitters have hit .259 with an OPS of .781.
Since May 16, Red Sox pitchers have a 3.22 ERA.
As frightening as it is, this team hasn't played up to its full capability yet.