SAN FRANCISCO — Minnesota Twins catcher-turned-first baseman Joe Mauer has some advice for San Francisco Giants All-Star Buster Posey: play catcher as long as you can, and enjoy doing it.

“There will be a day when he can’t catch anymore and a day where we can’t put the uniform on anymore,” Mauer said before the Twins played at San Francisco on Friday night. “He’s a special player and he’ll be able to make that transition if he wants to. I’d like to see him catch as long as he can.”

Minnesota is making a rare visit to San Francisco this weekend for a three-game interleague series, giving fans an even rarer opportunity to see two of the greatest hitting catchers of their generation play against each other, with one major twist: neither started at catcher in the opener.

Mauer, the 2009 AL MVP and a three-time batting champion, moved to first base this year after a concussion last August ended his season. Posey, the 2012 NL MVP and batting champion, is planning to catch for the Giants for the foreseeable future but has spent some time at first base the past couple years to rest his body during the season, including a nerve irritation in his lower back that sidelined him for two games in Colorado this week.

Kurt Suzuki was catching for the Twins, as usual, while backup Hector Sanchez was behind the plate for the Giants.

But make no mistake: Posey has no plans to move to first base permanently, at least not anytime soon. And manager Bruce Bochy, a former catcher, reiterated the Giants are paying him to be their starting catcher.

The debate about where Posey should play has still raged on in San Francisco since he suffered violent, season-ending left leg and ankle injuries in May 2011 — a year after winning NL Rookie of the Year honors. He came back better than ever to help San Francisco capture its second World Series championship in three years in 2012.

Mauer might relate to Posey’s predicament more than anybody. He played his first 10 seasons at catcher and, despite years of public pressure to change positions for fear of injury, he stuck with it until last season’s concussion.

Mauer, who said he probably had some undiagnosed concussions while playing quarterback in high school, called the lengthy recovery time “frightening.” Given the severity of the head injury, he said “it really wasn’t much of a decision” to turn in his catcher’s mask for a first baseman’s glove.

“It’s difficult anyway you look at it,” Mauer said. “I caught for 10 years and really enjoyed that position. That’s what I worked my whole life to be. I put in a lot of time at that position and I’m fortunate enough that I could go somewhere else and play. I miss it, definitely. But once you make that decision, you have to move on.”

There are also financial components, too, though both players have brushed that aside.

Mauer, now 31 years old, is less than halfway through a $184 million, eight-year contract. The 27-year-old Posey signed a $167 million, nine-year contract before last season.

But just as the Twins never forced Mauer to move, the Giants have never said publicly that they want Posey to change spots. And Posey, who started as a shortstop at Florida State, has said repeatedly that he wants to stay behind the plate because he likes being involved in the pitch-to-pitch strategy of the game — just as Mauer did.

“I miss calling the games. I miss being behind there,” Mauer said. “I don’t miss foul tips.”