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5/23/2014 10:48 P.M. ET

Cutter working well for Twins reliever Fien

SAN FRANCISCO -- With another scoreless inning in Wednesday's 2-0 win over the Padres, Twins reliever Casey Fien has made 18 out of 20 appearances this year without giving up a run.

Entering the Giants series, the 30-year-old righty had a 1.89 ERA and 0.84 WHIP (walks plus hits per inning pitched) in 19 innings while earning the trust of skipper Ron Gardenhire.

"He's gotten an opportunity here with us and he's taken it and ran with it," Gardenhire said. "He's always been very intense and now he came up with a pitch that kind of got him over the hump and he's running with it. He's throwing harder, he's pitching with a lot of confidence and he has the pitches to back it up."

After making 11 appearances for Detroit in 2009-10, Fien spent the entire 2011 campaign in Houston's farm system. But ever since adding a cutter to his arsenal, he has become a consistent force for Gardenhire since taking over a spot in the bullpen during the second half of the 2012 season.

"I think that's been what got me to the big leagues, for sure," Fien said of his cutter. "But I think my cutter against lefties is what's been behind my success this year, better than last year, and getting outs early."

Fien said he's enjoyed facing unfamiliar teams in Interleague Play like the Padres and the Giants. Since their left-handed hitters often aren't expecting to see a first-pitch cutter, he can often sneak it over the outside of the plate for called strikes.

"Especially teams that don't know me," Fien said. "Like San Diego, it worked perfect. Now with Detroit and Chicago, I've got to pitch them a little bit differently because they look for that. Especially the big lefties like [Adam] Dunn or [Alex] Avila for the Tigers."

Mauer hopes Posey can stay at catcher

SAN FRANCISCO -- When the Twins and Giants took the field Friday night for the series opener at AT&T Park, Joe Mauer and Buster Posey were the starting first basemen.

Over the past few years, both Mauer and Posey established themselves among baseball's elite catchers. But starting in 2014, Mauer moved to first base full time, while Posey continues to receive occasional starts at the position.

While the two players are in different situations -- Mauer was essentially forced into the role after enduring concussion problems last year -- the Twins first baseman said he hopes Posey can stay behind the plate.

"There will be a day when he can't catch any more and there will be a day when he can't put on the uniform any more," Mauer said. "But he's a special player and he'll be able to make that transition at the end of his career if he wants. I'd like to see him catch as long as he can and have a few more years after that, too."

Even though this marks Mauer's first full season at first base, he noted that many have suggested the position switch dating back to when he was 20 years old after he underwent knee surgery, so he knows what Posey is going through.

Friday marked the 33rd game for Mauer at first base this year, and manager Ron Gardenhire admitted that Mauer still needs to work on his relay technique, among other things, but that he's athletic enough to handle the position.

"I miss calling the games and being behind there," Mauer said. "I don't miss the foul tips, but I definitely miss calling the game and working with the pitcher, for sure."

Gardenhire said the Twins have also benefited from having a veteran catcher like Kurt Suzuki to ease the transition and not throw too much at young Josmil Pinto. As for giving advice to Giants manager Bruce Bochy on how to handle his situation with Posey going forward, the Minnesota skipper said, "Nope. Tell Bochy he's got it.

"I think he can figure it out; he's pretty good at what he does," Gardenhire added. "Boch knows; he was a catcher. He knows what he's going through. And it all comes down to the mindset of Posey -- he's got to want to do it. He's got to say, 'This is OK. I can handle it.'"

Worth noting

• Gardenhire said outfielder Josh Willingham is coming back strong as he recovers from a wrist injury that has kept him on the 15-day disabled list since April 6. Willingham went 3-for-20 in his first six games for Triple-A Rochester, but Gardenhire said the team would reassess the situation upon returning to Minnesota for Monday's homestand.

"His wrist is feeling good," Gardenhire said. "He's actually put some good swings up there. His numbers aren't great, but he's put some decent swings on there."

• Outfielder Sam Fuld (concussion) went to Target Field on Friday but the team said there was no progress to report.

Alex Espinoza is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.