BOSTON — The Minnesota Twins were lucky enough to face Jon Lester in the first game at Target Field, when the Red Sox left-hander was still struggling to find his form.

When they saw him again on Thursday night, Lester showed them why he’s the winningest young pitcher in baseball history.

Lester earned his fourth straight victory and his fifth career complete game, striking out nine to lead Boston to a 6-2 victory over Minnesota. He lifted his career winning percentage to .719 – the best ever for a pitcher with at least 100 starts.

“That’s great,” Lester said without a smile or other noticeable reaction. “But that’s just a testament to the teams that I’ve been on. It’s easy to pitch when guys score runs.”

Kevin Youkilis hit a three-run homer and an RBI double, Adrian Beltre also homered, and Victor Martinez had three doubles to help the Red Sox complete the two-game sweep.

A month after giving up four runs in five innings against the Twins in Minnesota, Lester (4-3) took a shutout into the eighth before allowing two runs – one earned – on six hits. He improved to 46-18 lifetime in a career that includes a no-hitter and a World Series clincher.

“He’s still the same Lester, man,” Twins second baseman Orlando Hudson said. “Power lefty, does a great job. Tell you what man, he’s tough. He’s real tough.”

The Twins have scored six runs total while losing their last three games to fall into a tie with Detroit atop the AL Central.

Francisco Liriano, who won his first four decisions to start the season, has now lost three straight starts. Liriano (4-3) left after giving up back-to-back doubles to Martinez and Youkilis with two outs in the fifth. The Twins left-hander allowed five runs on five hits and three walks, striking out six.

“It wasn’t a good performance by him,” Twins Manager Ron Gardenhire said. “A lot of pitches and not very many innings, and he really missed in some big situations. When you do that in this ballpark it ends up in the seats.”

Lester faced the minimum 12 batters in the first four innings and had a shutout going when Michael Cuddyer led off the eighth with a double, moved up on a groundout and scored on Delmon Young’s sacrifice fly to make it 6-1. The Twins scored an unearned run in the ninth after second baseman Dustin Pedroia botched a double-play ball.

“He was relentless,” Red Sox Manager Terry Francona said. “There’s a lot of ways for him to go right now and still attack the strike zone.”

Liriano went 3-0 with a 0.93 ERA in April. But he has allowed 16 earned runs in 232/3 innings in May.

Liriano, who hadn’t allowed a homer in 501/3 innings dating to last season, gave up Beltre’s solo shot in the second, then got into more trouble when he walked Pedroia with two outs in the third.

Martinez followed with a double, then Youkilis homered to center to make it 4-1.

Beltre reached base three times, doubling in the sixth and scoring on Joe Mauer’s passed ball.