Everyone loves Joe Mauer, as well they should. Given a normal growth curve, he will be an outstanding hitter. . .hell, he already is most of the time.
Of course, catcher growth curves are not always normal. The main unanswered question right now is how much home run power Mauer will develop. It's hard to remember considering Minnesota's pop-gun offense of recent years, but for most of their history the Twins franchise was renowned for offense: Killebrew, Oliva, Carew, Puckett, Hrbek. . .even the minor stars of Twins history like Bob Allison, Larry Hisle, Gary Gaetti, and Tom Brunansky tended to be power guys. But now it's pitching-and-defense all the way. That's good, but as a Twins fan I'd like to bring some of the power back, too.
For purposes of this Crystal Ball, I am going to assume that Mauer avoids further severe knee trouble in the immediate future. However, I will posit a major injury down the line, one that forces him to move to another position (probably first base) around age 30.
Although I continue to caution people not to take the Crystal Ball feature too seriously, I do think that Mauer's career (if he stays healthy) will look something like this.