Joe Mauer's eyes looked tired, his voice was strained, and he had to pause several times to cough, but the Twins catcher offered several reassurances Monday that he is dealing with pneumonia and nothing else.

"When they discovered pneumonia down at the Mayo Clinic [on Sept. 15], that's what they do, they check over everything," Mauer said. "That's what they came up with, and that's what they're treating."

It was the first time Mauer was available to the media since he last played on Sept. 14. Doctors told him to stay home during the Twins' last homestand, but he got clearance to return to Target Field on Monday, as the Twins opened their final three-game series against the Royals.

"If you don't treat something like this, it can linger, and it's definitely not what we want to do," Mauer said. "I have to come back strong and healthy [next season], just like any other year."

Mauer was asked repeatedly if he's concerned he's dealing with something more serious. At age 28, in the first year of an eight-year, $184 million contract, he was limited to 82 games and batted .287 with three homers and 30 RBI, while dealing with multiple injuries and ailments.

In April, Mauer went on the disabled list with what the Twins called "bilateral leg weakness." Mauer has since explained that he needed time to recover from his December knee surgery. Compounding his issues, the day he landed on the DL, he went to the hospital with a viral infection and eventually lost 15 to 20 pounds.

After missing 58 games, Mauer returned and played regularly -- at catcher, first base and DH -- before missing six games because a strained neck in late August.

Then, on Sept. 2 in Anaheim, Calif., he was out of the lineup because an upper-respiratory infection. Mauer said he had fluid in his ears and was having episodes of vertigo. After missing two games, he played in the next seven before heading to the Mayo Clinic.

"That whole infection [in Anaheim] -- that's how the pneumonia started," Mauer said. "I tried playing through it, and it turned into this, and was just advised by everybody that this isn't the right direction that we're supposed to go."

On Sept. 16, with Mauer home recovering, the Twins announced that he had "mild pneumonia." On Monday, a reporter made reference to "walking pneumonia," which is a mild form of pneumonia.

"I've never heard of walking pneumonia," Mauer said. "I have pneumonia."

Later when asked about concerns that he might have something more serious, Mauer said, "You started this interview off with a term I've never heard of [walking pneumonia]. People are going to put in their own two cents. ...

"The fact is, I have pneumonia. I'm dealing with it. I'm not over it yet. That's first on my list to take care of. Hopefully I can get strong and get ready for next year."

Manager Ron Gardenhire doesn't think Mauer needs any more motivation.

"Believe me, I think he knows what he needs to do," Gardenhire said. "Joe's a great player. He's been an MVP, an All-Star, a Gold Glover, a batting champion. His expectations are very high, so anything less than that -- less than .300 batting average and a chance to be a Gold Glover and a chance to be a batting champion -- is not satisfying to Joe."