When the 2012 season opens, it's likely that Canzler will be the team's starting first baseman ahead of LaPorta.
Canzler is a soon-to-be 26-year-old minor league vet who lacks the prospect pedigree of LaPorta, but he's turned himself into a guy who should be able to contribute at the big league level after hitting .314/.401/.530 at Triple-A Durham. Among International League players with 200 plate appearances, only Trevor Plouffe and Ryan Lavarnway had a higher OPS. Canzler played first, third, left and right for Durham, although his fielding percentage indicates he's stretched at third base. But with LaPorta coming off another disappointing season (.247/.299/.412), I would guess Canzler will be given the opportunity to win the first-base job. (A platoon isn't really feasible since both hit right-handed.)
I actually thought Canzler would be a nice platoon with Carlos Pena in Tampa, considering Pena hit .133 against left-handers in 2011. But the Jeff Keppinger signing made it tough to find room for Canzler on the roster.
Assuming the Rays go with 12 pitchers, their 13 position players probably look like this:
1B: Carlos Pena (L)
2B: Ben Zobrist (S), Jeff Keppinger (R)
3B: Evan Longoria (R)
If Joe Maddon wants to platoon with Joyce, he can slide Zobrist to right field and play Keppinger at second. That would probably give Fuld the edge over Guyer for the fourth outfield position, since he could spell Jennings against tough right-handers. The other option would be keep Guyer as a possible platoon partner for Joyce (or Scott at DH) and use Keppinger at first base against right-handers. And yet another option is to see if Brignac can win the starting shortstop job on a full-time basis, with Rodriguez serving as the starter at shortstop or first base against left-handers (over his career, he's hit .260/.360/.422 against left-handers but just .212/.278/.377 against righties). Brignac and Johnson are both regarded as superior fielders to Rodriguez, so if Brignac can at least hit like he did in 2010 (.256/.307/.385), the job will be his to win.
Anyway, as always Maddon has roster flexibility. I don't like the idea of Pena as a full-time first baseman, but it looks like the Rays will have options to ensure that he doesn't have to play every day against left-handers.