"My stuff at times was good and at other times I was trying to do too much, overthrowing the ball a little bit," Lester said.
Lester (13-7) has allowed two runs and six hits in 13 innings in his past two starts to beat Kansas City and Tampa Bay. He is 5-1 with a 1.30 ERA in seven career starts against the Royals, including a no-hitter on May 19, 2008.
Carl Crawford and Darnell McDonald hit solo home runs for the Red Sox. McDonald replaced Jacoby Ellsbury, who missed his second straight game with a contusion in his back after being hit by a pitch Friday.
"It's nice to know when those guys are out you have other guys to fill in and do a good job," Lester said. "That's big for us, a confidence-booster definitely. Guys that filled in those spots did a good job."
Varitek's two-out triple rolled to the right-center fence, allowing Jed Lowrie to score in the fifth to break a scoreless deadlock. Lowrie led off the inning with a single and moved to second on a Crawford ground out. Varitek's triple was his first since June 24, 2007 at San Diego off Jake Peavy.
How did it feel?
"Not so good," said Varitek, who was icing both knees at his clubhouse stall. "I'm just spacing them out. With two outs, it didn't look like it's something I shouldn't have any problem getting to (third)."
Red Sox manager Terry Francona joked "speed never takes a day off."
"It's not like Jacoby and Carl, trust me," the 39-year-old Varitek said.
"It's not often you see Tek get a triple," Lester said.
McDonald, who had three hits, hit his fifth home run of the season in the sixth on an 0-2 pitch from Royals rookie left-hander Danny Duffy (3-7). Aaron Crow gave up a home run to Crawford, his eighth, in the seventh inning.
Duffy gave up two runs on five hits in six innings, while striking out three and walking two. He has lost four August starts since a July 31 victory at Cleveland.
Johnny Giavotella led off the Royals seventh with a triple and scored on Mike Moustakas' single for the only run off Lester. He was replaced by Daniel Bard after 113 pitches with two runners on base. Bard retired the next three hitters.
"It's nothing unexpected from him," Lester said of Bard's performance. "He's done it since he's been up here. It's big to have a guy like that in our bullpen. That's what he's done all year. It makes your job a little easier as a starter, knowing you have those guys down there."
The Royals loaded the bases on two walks and a Lowrie error in the second, but Lester retired Alcides Escobar on a comeback to end the inning.
"Jed makes that play basically 10 out of 10 times," Lester said. "You have to pick your teammates up sometimes like they pick you up. I was able to minimize the damage."
Lester did not allow a hit until Perez's single with two out in the fourth.
"Jon Lester is bona fide," Royals manager Ned Yost said. "He's a premier lefty in this league and he showed why."
It is questionable whether Ellsbury will return Monday when the Red Sox open a four-game series at Texas. "It doesn't make a lot of sense to get him back out there too early," manager Terry Francona said. "He's still pretty sore." The Royals are off Monday before playing 17 of their next 20 games on the road. RHP Bobby Jenks, who has been on the disabled list twice this season with back tightness, is scheduled to throw 20 to 30 pitches Monday in a simulated game at the Red Sox complex in Fort Myers, Fla. ... DH David Ortiz, who has missed the past seven games with bursitis in his right heel, is hitting off the tee and soft toss in the cages, but is still wearing a boot on his foot. ... Red Sox LHP Erik Bedard, who starts Monday, is winless in his past eight starts against the Rangers, although he has allowed three earned runs or less in each of his previous four starts. ... Royals LHP Tim Collins got the final out of the eighth on his 22nd birthday.