Joe Mauer struck out three times on Sunday. It was like watching a bear starve in a stream of salmon.

Mauer isn't the Twins' problem. He's hitting .342, the only regular on the team batting over .300. He ranks fifth in the American League in batting average and third in on-base percentage.

He's played well behind the plate, improving his throwing this season, and he's played often, appearing in 38 of 40 games. Sunday, he wound up catching in a game that started at 1:10 p.m. and ended at 7:25 because of a three-hour rain delay, and went 0-for-4, breaking a 15-game hitting streak.

Mauer sat out Friday because of a sore back but didn't beg out of a day game on Sunday or during the delay. "I was worried about that," manager Ron Gardenhire said.

What's strange is that while Mauer is hitting like Mauer, and playing as often as he ever has, he's striking out like a free-swinging power hitter. He has struck out 39 times in 155 at-bats this season, or 25 percent of the time.

Last year, Mauer struck out 88 times in 545 at-bats, or 16 percent of the time. Before last season, the most times he had ever struck out in a season was 64, in 2005, in his first full season in the big leagues, and 63, in 2009, when he became the American League Most Valuable Player.

In 2009, despite those strikeouts, Mauer posted his career-best average, on-base percentage and slugging percentage despite his strikeouts.

Or maybe that's the wrong way to look at it. While strikeouts are bad in and of themselves, with Mauer they might indicate an aggressive mind-set that can pay off with extra-base hits and RBI.

In the eighth inning Sunday, Mauer came to the plate with the bases loaded and two outs, and struck out on a pitch out of the strike zone. He usually would take that pitch.

"He's really swinging," Gardenhire said. "He's letting it fly a lot more than he used to. And swinging first pitch more than he's used to. That's not normal. But that says that he's being aggressive and going after the ball. He knows we need him to do that."

Josh Willingham is hitting .197. Trevor Plouffe hit cleanup on Sunday despite having hit only four home runs. Chris Parmelee is hitting .198, Brian Dozier is hitting .212 and Aaron Hicks is hitting .139. Suddenly, nobody is blaming former hitting coach Joe Vavra for the Twins' lack of run production. "We can't drive in a run right now," Gardenhire said.

Even after his 0-for-4, Mauer's slugging percentage is .490 this season. If he finished the season at that mark, it would be his best slugging percentage since his MVP season.

"He's just trying to drive the ball a little more," Gardenhire said. "I start noticing that when he starts really taking rips on the first pitch.

"He's driving the ball the other way real good. These guys throw him out and over the plate an awful lot, and he's taking a rip. I don't know if his power numbers are going to go up, but I know he's taking some rips."

That at-bat in the eighth inning wasn't pretty, but it evoked memories of debates regarding other hitters through the years. Ted Williams refused to swing at a pitch out of the strike zone, even when Bostonians begged him to sacrifice average and walks for power numbers. But would Ted Williams have been one of the greatest hitters of all time if he had changed his approach?

Mauer was not available in the clubhouse after the game to answer questions on the subject, but Minnesotans might get to live through a test case this summer. One of the best hitters in the game and best-hitting catchers of all time seems to be subtly altering the approach that has won three batting titles.

Joe Mauer swinging in anger? As Mauer might say: "Jeez."

Jim Souhan can be heard weekdays at noon and Sundays from 10 to noon on 1500 ESPN. His Twitter name is @SouhanStrib. jsouhan@startribune.com