Twins star Joe Mauer underperforming at new position

As Joe Mauer walked back to the dugout, the bat in his hand and a sour look on his face, there were boos from the Minnesota crowd.

Mauer struck out to end the inning, with a runner on third base in the seventh on Wednesday and the Twins trailing 1-0. Everybody does this, of course, in a sport with a 30 percent success rate at the plate long proven to be a benchmark of excellence.

Failures this year have piled up faster than usual for Mauer, a six-time All-Star, three-time American League batting champion and one-time A.L. MVP.

“I’m a heck of a lot more frustrated than they are,” Mauer said that night, when asked about those jeering fans.

The sound of those boos has been jarring, considering he’s the hometown guy from St. Paul with the hitting skills to build a .321 career batting average, the best among all active players with at least 3,000 plate appearances. Minnesotans are fiercely proud of and protective of their natives, so Mauer figured to have a lifetime pass in the popularity department.

After signing a $184 million, eight-year contract extension in 2010, though, he has become a more-frequent target of criticism from fans frustrated by the team’s struggles the past several years.

The 28 home runs he hit in 138 games in 2009 were a one-year wonder. Lingering lower-body injuries limited him to 82 games in 2011. This season, his on-base-plus-slugging percentage was at a career-low .704 entering the weekend series. Mauer is also on pace to blow by his career-high strikeout total of 89 set last year.

“I feel pretty good actually, which is even more frustrating,” he said.

Mauer reluctantly gave up his job as the catcher to better protect himself from another concussion, after missing the final six weeks of last season following a foul tip that hit him in the head. The loss to the Twins of Mauer’s intelligence and defense behind the plate was supposed to be trumped by an increase in his availability and production at a less-taxing position (first base, where he has played 39 times this season).

He missed five games with back spasms earlier this month, but since then he said he feels fine. The problem has been these paltry totals: nine extra-base hits and 15 RBIs through Thursday.

Cain put on DL

San Francisco Giants pitcher Matt Cain has been placed on the 15-day disabled list with a strained right hamstring. The move was made retroactive to May 22.