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6/26/2013 4:08 P.M. ET

Farrell: 'We've got to get Jon Lester back on track'

BOSTON -- If the Red Sox are going to achieve the level of success they hope, Jon Lester needs to improve.

That was the message manager John Farrell communicated before Boston's game against Colorado on Wednesday at Fenway Park.

After starting the year 6-0 with a 2.72 ERA, Lester has just one quality start in his last seven outings and has recorded a 7.30 ERA.

"We've got to get Jon Lester back on track," Farrell said. "There's no denying that. He'd be the first to admit to you as well."

Perhaps just as concerning, Lester, who prides himself on pitching deep into games, hasn't made it through six innings in his last three starts. That would spark health concerns for some, but Farrell said Lester's issues are more mental than physical.

"He's sound healthy," Farrell said. "I think he's doing a typical job of repeating his delivery. I think it's the consistency of execution, particularly with two outs when you get in a situation with men on base. There's been, I think, at times he'll rush a little bit to try and get through a given inning, and that might cause that inning to be prolonged."

Lester is scheduled to start against the Blue Jays on Thursday night, and Farrell is confident he'll get back on track.

"I don't think Jon Lester's stretch he's on will continue," Farrell said. "He's too talented of a pitcher."

Mortensen activated off DL; Beato optioned to Minors

BOSTON -- The Red Sox activated reliever Clayton Mortensen from the 15-day disabled list and optioned Pedro Beato to Triple-A Pawtucket on Wednesday.

Mortensen, 28, made three relief appearances in Pawtucket as part of a rehab stint stemming from a strained right groin and gave up two runs in four innings with two walks and four strikeouts. The right-hander is 1-2 with a 5.34 ERA with Boston this season in 30 1/3 innings.

Beato's trip to the Major Leagues was brief. He was called up Tuesday to give Boston some added depth in the bullpen, and after pitching a scoreless ninth inning in Tuesday's 11-4 win over Colorado, the 26 year-old was sent back to Pawtucket. In each of his three relief appearances with the Red Sox this season, he hasn't allowed a run.

In Pawtucket, he's 5-1 with a 1.83 ERA in 20 relief appearances.

Michael Periatt is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.