MVP 2015: Sizing up the finalists for MLB's top award

On one side, there's the kid from whom we expected the world. On the other, a 29-year-old who was traded and had to switch positions before he became a star. On Thursday, though, they could both be MVPs.

Bryce Harper and Josh Donaldson highlight this year's MLB Most Valuable Player races. They're the favorites in their leagues, with Harper, the young Washington Nationals star, more of a sure thing. Donaldson, the Toronto Blue Jays third baseman, will face some challenge from Mike Trout — just like any would-be AL MVP will for the next decade.

[Related: Transformation complete: Cubs' Jake Arrieta takes home NL Cy Young]

The awards will be handed out at 6 p.m. ET on MLB Network, based on votes from the Baseball Writers Association of America. We know the three finalists in the AL and NL, so here's a look at each player's season, the case for them and the case against them:

AMERICAN LEAGUE

Lorenzo Cain — Kansas City Royals

In brief: He was the best player on the best team in the AL, and thus Cain is a finalist. He hit 16 homers and drove in 72 runs, neither the type of power numbers you generally associate with an MVP, but the Royals also play a different brand of ball. Cain is among the best outfielders in the game and he hit .307.

Case for: You'd have to buy into his role in the Royals success to put Cain atop your ballot. He's probably the best defender of the bunch too.

Case against: His offensive numbers just don't compare. Not only are we talking about homers and RBIs, but his on-base percentage was .361 compared to, for instance, Trout's .402.

Josh Donaldson — Toronto Blue Jays

In brief: After a surprising trade sent him from the Oakland Athletics to the Toronto Blue Jays, Donaldson feasted at a hitter-friendly park in Toronto. He hit 41 homers, drove in 123 runs, scored 122 more while hitting .297.

Case for: His is a tried-and-true MVP case. The numbers are there. He helped his team improve and win the AL East. Really, though, a vote for Donaldson is a vote for RBIs. That's where he was far-and-away ahead of the competition. He and Trout were about the same in homers and batting average. But when you look at RBIs, things heavily favor Donaldson — 123 vs. 90.

Case against: So about RBIs — they require some help from your teammates getting on base. Some voters will pick Trout because of that and wonder how much of Donaldson's production was aided by a potent Toronto lineup.

Mike Trout — Los Angeles Angels

In brief: Trout had another fantastic season, which is the norm for him. He hit 41 homers, drove in 90 runs, got on base 40 percent of the time, slugged .590 and played good defense.

Case for: Trout wins if you value OPS, basically. His on-base percentage topped Donaldson's (.402 to .371) and his slugging percentage was better too (.590 to .568). Trout walked 19 more times.

Case against: It's really the RBIs. Donaldson had 33 more than him. Do Trout's other numbers make up for that difference? That's the question voters had to ask themselves.

NATIONAL LEAGUE

Paul Goldschmidt — Arizona Diamondbacks

In brief: Goldy continues to be across-the-board great for the D-backs. His stellar 2015 numbers include 182 hits, 110 RBIs, a .321/.435/.570 slashline with 33 homers. He also played Gold-Glove defense at first base.

Case for: You have to pick and choose your categories, because Harper leads most of the big ones. But here's where Goldschmidt was better: He drove in more runs, played in 159 games to Harper's 153 and had a surprising 21 stolen bases

Case against: Harper bested him in batting average, on-base and slugging percentage, homers and runs scored.

Bryce Harper — Washington Nationals

In brief: All the hype, it came true this year. Harper, in his age-22 season, hit 42 homers, drove in 99 runs, hit .330 and led the NL in on-base and slugging percentage, proving he can hit for power and average. He also scored an NL-high 118 runs.

Case for: Harper out OBP'd Votto, which is his game. He out-homered Goldschmidt, which is one of his strengths. He also led the NL in WAR — and not just by a little. Harper's fWAR was 9.5, more than two full wins better than Votto and Goldschmidt (both 7.4).

Case against: You have to nitpick to find anything wrong with Harper's year. First, his team didn't make the postseason, but none of the other finalists' teams did either. Harper also finished fifth in RBIs. If you hold that against him, well, that's a you-problem.

Joey Votto — Cincinnati Reds
In brief: Votto had a stellar season for a bad Reds team. His .314 batting average was great. His .459 on-base percentage was fantastic, as it usually is with Votto. He hit 29 homers and was a seven-win player, according to Fangraphs.

Case for: There aren't many meaningful stats that favor Votto over Harper or Goldschmidt. But he did strikeout less frequently than both of them. He also led the NL in walks. His judgment remains on point.

Case against: Harper topped him in most every important offensive category, including slugging more than 100 points higher.

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Mike Oz is the editor of Big League Stew on Yahoo Sports. Have a tip? Email him at mikeozstew@yahoo.com or follow him on Twitter! Follow @MikeOz