But after weighing the risks, Mauer, who has been symptom-free from the concussion since late October, determined that it would be in the best interests of both him and the Twins for a position change. He informed the club of his decision last week.
"This was one of the tougher decisions I've had to make but also probably one of the easiest," Mauer said in a conference call along with Twins general manager Terry Ryan. "It was a tough decision because I love catching and it's something I've worked hard at my whole life to become the best catcher I could be. So I'm a little disappointed my catching career had to end like this.
"As far as it being an easy thing, given the magnitude of the decision, I took my time just to make sure I was making the right decision for myself, my family, my career, my teammates and the organization. So I look forward to the challenge and getting back on the field."
Mauer, 30, was in the midst of another strong season but took a foul tip off his catching helmet on Aug. 19, and missed the rest of the season.
He finished the year with a .324/.404/.476 slash line with 11 homers, 35 doubles, 62 runs and 47 RBIs in 113 games. He was the American League's starting catcher in the All-Star Game and won his fifth Silver Slugger Award while also being named a finalist for a Gold Glove Award.
But the concussion ultimately altered Mauer's career course, as he said the risks of staying behind the plate were too much to ignore.
"If I were to have another concussion, the symptoms would probably last as long or even longer," Mauer said. "What concerned everybody involved was how long it took me to be symptom free."
Playing first base isn't completely foreign to Mauer, as he appeared in 18 games there in 2011, 30 in '12 and eight this year.
The move also will fill a big hole for the Twins after they traded first baseman Justin Morneau to the Pirates at the end of August. Morneau is a free agent but is unlikely to sign with the Twins now that Mauer will be playing first.
"I never say never, but we have a first baseman here," Ryan said. "I'll never say it's not a possibility, but it might be improbable."
The Twins have depth at catcher with 24-year-old Josmil Pinto emerging as an offensive force during his short time with the team as a September callup. After hitting .309/.499/.482 with 15 homers and 74 RBIs in 126 games between Double-A New Britain and Triple-A Rochester, Pinto batted .342/.398/.566 with four homers, five doubles and 12 RBIs in 21 games with Minnesota.
Veteran backstop Ryan Doumit also is on the roster, while 25-year-old Chris Herrmann saw time at catcher and in the outfield this year.
But Ryan said the Twins will keep their options open at catcher, as they could still look to the free-agent market even though starting pitching remains the club's top priority this offseason.
"We have a pretty good group back there, but it doesn't stop us from looking elsewhere," Ryan said. "It's always a possibility."
The Twins are hoping the move will keep Mauer healthy, as he has played in more than 140 games just once over the past five seasons while dealing with knee issues, back issues and the concussion.
Mauer won't be the prototypical slugging first baseman, as he hit 11 homers last year and hasn't come close to replicating the 28 homers he hit during his Most Valuable Player season in 2009. But Mauer's .404 on-base percentage ranked second among qualified big league first basemen this past season while his slugging percentage ranked 10th.
Mauer is signed through 2018 at $23 million per season after inking an eight-year, $184 million deal before the 2010 season.
"I think I'll be in the lineup more, that's for sure," Mauer said. "I won't have to be squatting behind the plate and taking foul tips and things like that. I anticipate playing a lot more, and I think if I'm allowed to do that, I can put up some bigger numbers."