For Lester, success brings more challenges

"The approach is still the same," Lester said. "They know I'm going to come after them with fastballs in and cutters in and they know what I've got. I think just with having a year like last year, especially being a part of this organization, you have a target on your back.

"Teams want to beat you. All five guys in this rotation, I think teams come in every series and they know that we're going to give our best, and they're going to give us their best.

"I don't think it has anything to do with [knowing more about him]. I faced the Jays [Sunday], I didn't pitch them any differently than I did [10 days earlier]."

On May 21, Lester allowed Toronto one run in 6 1/3 innings. After Lester humbled them twice, some Blue Jays were baffled at Lester's struggles this season (4-5, 5.65 ERA).

"You kind of wonder how a guy like that comes into the game with a [6.07] ERA with the kind of stuff that he has," Toronto outfielder Vernon Wells said Sunday. "When he's on, it's difficult. And when you see the kind of numbers he put up against us, especially with the strikeouts, it was impressive."

Strikeouts have been a constant for Lester. His 10.2 strikeouts per nine innings rank second in the American League, behind only Detroit's Justin Verlander (11.7). Lester said he would sacrifice strikeouts for longer outings, and his wish may depend on the particular day and opponent.

"With his stuff, there will be a lot of strikeouts," manager Terry Francona said. "But there's going to be games when his two-seam [fastball] is working, and they're putting it in play, and he's not going to have a lot of strikeouts, and we're thrilled. Sometimes it's not only how he's pitching, but how they're approaching him."

"It's nice to come back and not have to carry the water," he said.

The newest member of the Red Sox bullpen, adhering to tradition, carries a backpack crammed with water bottles to the bullpen. That task now falls to Daniel Bard.

The transition has been positive on the mound as well. Masterson's heavier workload as a starter increased his stamina, allowing him to pitch at least two innings in each of his three relief appearances, during which he has allowed two earned runs in 7 1/3 innings.

Last season, Masterson made the switch from starter to reliever in the minor leagues. Relying on that experience, he has had no significant issues during his transition this year.

"It's gone just as well as I hoped," Masterson said. "I think we're still overall just getting that feel. You know, working out and then pitching that day, getting the body accustomed to that. I think we're ready to go. It's not going to be perfect by any means."

Adam Kilgore can be reached at akilgore@globe.com