KANSAS CITY, MO. - The boos are getting louder at Target Field, and Joe Mauer knows it.

It's been a brutal season for the Twins, caused by a perfect storm of injuries and roster-wide failure, but it's been particularly disappointing for Mauer, the hometown icon, in the first year of his eight-year, $184 million contract.

The team is 59-87, and Mauer has played only 80 games, batting .290 with three homers and 30 RBI.

"I understand that I'm probably going to get more of [the criticism] than anybody in this clubhouse," Mauer said. "Just given the fact that I'm from [Minnesota], I have a big contract -- all that stuff. So I'm going to take a lot of heat."

Mauer, who has started only 46 games at catcher, has heard the commentary calling him soft and questioning his desire to play.

"Obviously, I haven't had the numbers I wanted to," Mauer said. "Our team's won-loss record is not where we want to be. You can criticize me for that, but don't criticize someone's work ethic or character. That's where I have a problem."

Mauer, 28, is focused on finishing the season strong and rebuilding his body this winter so he can become a full-time catcher again and still get additional at-bats at first base or designated hitter.

Teammate and close friend Justin Morneau said he thinks Mauer's story would be playing out differently if the public fully understood the facts. The narrative became muddled, Morneau believes, when the Twins diagnosed Mauer with bilateral leg weakness on April 14.

That vague diagnosis -- described later by General Manager Bill Smith in its simplest form as "weakness in both legs" -- created a frenzy of speculation that Mauer might have a serious illness, as he spent 58 games on the disabled list.

"Joe's not one to make excuses," Morneau said. "The reality is, he tried to come back too soon from knee surgery. Could [the Twins] have helped him out if they said he never built back his strength, instead of calling it bilateral leg weakness? I think it would have been a lot different if they said, he tried to come back too soon so he could help our team win."

Chain of injuries

Mauer traces his troubles to April 30, 2010, in Cleveland, when he jammed his left heel on first base, suffering a deep bone bruise. Realizing it was an injury that wouldn't fully heal all season, he returned after missing seven games.

Compensating for the heel injury, Mauer soon felt other body parts aching, including his left hip. His hitting and throwing mechanics deteriorated. A lefthanded hitter, Mauer wasn't pushing off his back leg with the same strength, sapping his power. His right shoulder hurt, too.

The move from the Metrodome to Target Field did him no favors offensively. After hitting 28 home runs during his 2009 American League MVP season, Mauer hit nine last year, including one at home.

Mauer finished the year with 137 games played, and he batted .373 in the second half, finishing eighth in the MVP voting.

But on Sept. 19, he re-injured his left knee running to first base. He returned for the playoffs but was clearly hobbled in the Yankees' three-game sweep. Mauer had arthroscopic surgery on the same knee in 2004, and this time, after numerous medical consultations, he didn't have surgery until mid-December.

"Do I wish I would have had it earlier? Of course," Mauer said. "But at the time, myself, the organization -- we felt that was the best route."

With a shortened window to get ready for the April 1 season opener, Mauer still was rehabbing for most of spring training. He played in a few exhibition games and crossed his fingers that he'd be able to regain leg strength during the season.

"He started the year behind the 8-ball," Morneau said. "He's been playing catch-up ever since, and the position he plays doesn't allow him to get stronger during the year."

Mauer knew he was going backward by the season's second series. On April 14 with the Twins at Tampa Bay, he came down with a viral infection. That night, the Twins announced they were placing Mauer on the 15-day disabled list because of bilateral leg weakness.

"The truth kind of gets lost really quickly," Mauer said. "I was unavailable [to the media] for two days because I was in the hospital. When bilateral leg weakness came out, I really don't know where that term came from."

Asked if the team regrets that diagnosis, Smith said, "No, that's in the past."

A weakening reputation

Mauer said he lost between 15 and 20 pounds because of the viral infection. He arrived at spring training weighing about 230, but it was a much softer 230 than he preferred because the surgery had limited his workouts.

As the Twins spiraled 20 games under .500 by June 1, they were very guarded with their updates on Mauer, and he was largely invisible to the media.

Rumors swirled that Mauer had a crippling disease, but he and the Twins have insisted that's not the case. He was determined to come back as a full-time catcher, and at the time, he hadn't played any other positions.

Mauer finally returned June 17, and when Morneau needed neck surgery, the Twins persuaded Mauer to play first base.

In recent weeks, Mauer has missed six games to a sore neck and two games because of an upper-respiratory infection, but on Sunday in Detroit, he was the only Opening Day starter in the Twins lineup.

"It's just been a grind to get on the field, physically," Mauer said. "There hasn't been one game this year where I was like, 'Wow, I feel good.' You're trying to get on the field to play for your teammates, for your organization, to help this ballclub win."

Mauer said he believes he's making progress physically now, especially with his left knee. He has spoken to people about tweaking his offseason workout program. Right now, he weighs about 220 pounds.

"We can talk about weight, but it's putting on good weight -- strength and things like that," Mauer said.

Twins insiders don't question Mauer's work ethic. He's often the first player in the clubhouse and last to leave. He goes through an extensive training program each day, but some have wondered if Mauer should focus more on weightlifting and less on flexibility.

Perry Castellano, the Twins strength and conditioning coach, monitors Mauer's offseason progress in Fort Myers, Fla.

"He's known me since I was 18 years old," Mauer said. "He knows how my body's working and what injuries I've been dealing with. I'll rest and let my body heal, and then I'll work out with Perry in Florida again. I'll have a good strength base before heading to spring training."

Mauer hopes to catch at least 120 games next year, and now he knows first base is an option, too.

"Joe Mauer's an All-Star, a high-impact player, and this has been a very frustrating year for him," Smith said. "I have every belief and expectation that he's going to attack his offseason program, and he's going to do everything he can to come to camp in great shape."

Mauer also knows he needs to be more forthcoming to the media about his injuries.

He was hesitant in the past, he said, because he didn't want opponents to have an advantage. Other teams are bound to try for more stolen bases when they know a catcher's hurting.

"But obviously, if I can't play, you should know why I can't go on the field," Mauer said.