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7/24/2014 8:33 P.M. ET

Gibson not likely to make next start

MINNEAPOLIS -- Right-hander Kyle Gibson, who has been bothered by lower back stiffness, is likely to be ruled out to start on Saturday against the White Sox.

Gibson saw his scheduled start on Wednesday pushed back until Saturday after suffering back stiffness while throwing his bullpen session on Monday. He played catch on Thursday, but indicated he's likely not going to be ready for Saturday.

"The likelihood of him starting on Saturday isn't very good," Twins manager Ron Gardenhire said. "He did play catch today and is feeling better, but more than likely we'll have to find a starter for Saturday and have him go on like Tuesday."

Left-hander Logan Darnell, who is on the 40-man roster, is considered to be the favorite to be recalled from Triple-A Rochester to make the spot start on Saturday. Darnell, who has a 3.43 ERA in 17 starts at Rochester, last started on Sunday, giving up two runs on six hits over 6 1/3 innings against Norfolk.

Infielder Jorge Polanco, who was recalled from Class A Advanced Fort Myers on Thursday after the Twins traded Kendrys Morales to the Mariners, is likely to be optioned to make room for Saturday's starter.

Coaches to shift as Molitor heads to HOF induction

MINNEAPOLIS -- Twins coach Paul Molitor is heading to the National Baseball Hall of Fame induction in Cooperstown, N.Y. this weekend, and will be replaced on the staff by Minor League instructor Sam Perlozzo.

Molitor, who was inducted into the Hall of Fame in 2004, has been coaching first base recently, as third-base coach Joe Vavra has been sidelined with a torn labrum in his left hip, so first-base coach Scott Ullger has moved over to third base.

Perlozzo, who served as manager of the Orioles from 2005-07, will serve as first-base coach from Friday to Sunday in Molitor's absence.

"I've known Sammy for a long time," Twins manager Ron Gardenhire said. "He was my roommate and my manager while in the Mets system."

Gardenhire added that Vavra, who was diagnosed with his hip injury over the All-Star break, is still deciding whether or not to undergo surgery. But Vavra isn't expected to coach third base again this season either way.

"Scotty is probably going to be over there the rest of the season," Gardenhire said. "I don't think we'll put Joe back out there."

Pressly makes way back to Twins' bullpen

MINNEAPOLIS -- Right-hander Ryan Pressly was a fixture in the bullpen for the Twins last season as a Rule 5 Draft pick, but didn't join the Twins this season until Thursday, when he was recalled from Triple-A Rochester after Matt Guerrier was designated for assignment.

Pressly, 25, posted a 3.87 ERA with 49 strikeouts and 27 walks in 76 2/3 innings as a rookie last season. But he didn't break camp with the Twins to open the season and spent the year at Triple-A Rochester, where he also put up strong numbers.

The reliever had a 2.98 ERA with 63 strikeouts and 21 walks in 60 1/3 innings with Rochester before being called up Thursday. He found out he was getting promoted to the Majors from Rochester manager Gene Glynn before Wednesday's game.

"Getting called up to the big leagues is what you've worked hard for and what you want to do," Pressly said. "I was excited. Geno told me and everybody in the clubhouse gave me a big hug. So it was really exciting."

Twins manager Ron Gardenhire said it was difficult to part ways with Guerrier, who pitched in Minnesota from 2004-2010 before rejoining the club this season. But he added that he was excited to add Pressly to the bullpen.

"Press threw really, really well for us last year," Gardenhire said. "He's been throwing really well down there with good velocity. He attacks the strike zone and has a great curveball. He's in great shape."

Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, and follow him on Twitter @RhettBollinger. This story was not subject to the approval of Major League Baseball or its clubs.