To be blunt, the conversation begins and ends with Miguel Cabrera and Mike Trout.
Cabrera is 2 HR away from leading the AL in all 3 Triple Crown categories. He's been having a ridiculous month of September, hitting .373 with 7 HR, 20 RBI, and a 1.223 OPS.
Trout, on the other hand, is tailing off a bit towards the end of his rookie year, only hitting .274 this month with only 3 RBI.
Trout is still the hands down favorite so far, however, because the season is more than just September.
Trout leads all of baseball with an incredible 10.3 WAR, meaning he is worth 10 more wins than his replacement. In terms of value, that makes him the most valuable player in the AL, and even all of baseball, by far. Yadier Molina and Robinson Cano are tied for 2nd, with 6.6.
Cabrera's hitting numbers might be slightly better than Trout overall, but it is Trout's other abilities that put him over the top.
Trout leads all of baseball with 46 steals, has only been caught 4 times, and is also arguable the best outfielder in the game. Cabrera, on the other hand, is he polar opposite of a base stealing threat, and is a mediocre fielder, despite playing third base, a far easier defensive position.
Right now, Trout is the logical choice for MVP, even if Cabrera DOES end up with the Triple Crown. Don't shed a tear for Cabrera, though. It has happened before. Ted Williams won TWO Triple Crowns, and didn't come away with the MVP either time.
Barring a huge meltdown by Trout and an otherworldly performance by Cabrera over the next couple weeks, Mike Trout should join Fred Lynn (1975) and Ichiro Suzuki (2001) as the only players ever to win the Rookie of the Year and MVP awards in the same season.