As the recent Hall of Fame elections show us, evaluating baseball talent -- even Hall of Fame talent -- remains an imperfect, tricky science. John Smoltz, Randy Johnson and Pedro Martinez were all traded as young players: Smoltz while still in the minors, Johnson after his brief major league debut with the Expos and Martinez after his rookie season with the Dodgers. (Yes, the Expos could have had Johnson and Martinez in their rotation.)

Josh Donaldson is unlikely to become a Hall of Famer, but he's certainly in the midst of one of the most unusual careers I can remember. Look at where Donaldson stood entering the 2013 season. The one-time minor league catcher, who had been acquired from the Cubs in 2008, was entering his age-27 season and had appeared briefly with the A's in 2010 and then hit .241/.289/.398 in 75 games in 2012, playing regularly at third base down the stretch. Still, that batting line hardly indicated a player who was about to blossom into one of the best players in the league.

Donaldson became Oakland's starting third baseman in 2013 and hit .301/.384/.499 with 24 home runs and 93 RBIs while flashing outstanding defense at third base. He finished fourth in the MVP voting that season. Freed from the constraints of catching -- he's talked about how being a backstop in the minors was stressful because he worried about how to handle the pitching staff -- his bat finally developed. He showed surprising quickness and athleticism at third base. In 2014, he had another strong season, hitting .255/.342/.456 with 29 home runs and 98 RBIs, and finished eighth in the MVP voting.

The analytical methods loved Donaldson's two standout seasons. Baseball-Reference values Donaldson at 15.4 WAR over those two years, second among position players behind only Mike Trout; FanGraphs rates him third behind Trout and Andrew McCutchen. The MVP voters agreed that Donaldson has been one of the league's elite performers.

Then the A's traded him to the Blue Jays in November, a controversial deal considering that Donaldson is just entering his first year of arbitration and has four seasons remaining until free agency. Why would Oakland GM Billy Beane trade a still-inexpensive player, one of the best in the league?

The primary reason was that the A's wanted roster depth, so they acquired four players, three of whom could help in 2015. The second reason is more speculative: Does Beane think Donaldson has peaked? Some suggest that because Donaldson was a late bloomer he's also likely to decline more quickly. As the old Branch Rickey saying goes, trade him a year too early rather than a year too late.

The trouble with proving or disproving the hypothesis he has already peaked is that Donaldson's career arc is so unusual that there just aren't other players like him. I went searching for players since 1950 who were among the best in baseball in their age 27-28 seasons but who hadn't done much before that to see if there was somebody comparable -- and then to see how those players aged.

First, I was surprised to see where Donaldson ranked: His 15.4 WAR puts him tied for 13th in age 27-28 value with Chuck Knoblauch, just behind Alex Rodriguez, Ken Griffey Jr. and Eddie Mathews and just ahead of Chase Utley, Mike Schmidt and Joe Morgan. Most of the players in the top 50 are Hall of Famers, future Hall of Famers or near Hall of Famers such as Dave Parker and Dale Murphy.

Anyway, I did find a few similar players. Let's take a look.

George Foster (14.3 WAR at 27-28): Foster is a bit of a stretch to include here. He actually made his debut with the Giants in 1969 when he was just 20 and got a chance to play regularly in 1971 when he was traded to the Reds. He didn't play well, played sparingly in 1972 and spent most of 1973 in the minors. He had his breakout season in 1975, when he was 26, not 27, and also had played well in a part-time role in 1974 -- thus my reluctance to include him. Anyway, he remained a good player through age 32, when he signed with the Mets as a free agent and went downhill (as Mets fans well know).

Alex Gordon (13.5 WAR at 27-28): Gordon did have his first big season in 2011 at age 27, but had spent all or parts of the previous four years in the majors and was worth 4.8 WAR over his first two seasons. So he didn't exactly come out of nowhere, although he had spent much of 2010 in the minors. Gordon has continued to play well at age 29-30, although has batting numbers haven't quite matched his age-27 level of production.

Edgar Martinez (11.6 WAR at 27-28): This is the best match on the list. A late bloomer in the minors, Martinez was then held in Triple-A for an extra couple of years as the Mariners played Jim Presley at third base because they didn't think Martinez had the arm to play there. Finally given a chance to start in 1990 at age 27, he hit .302 and then .307 in 1991 and then won a batting title, with a .343 average, in 1992. He was one of the best hitters in the league for many years after that.

Brian Giles (10.6 WAR at 27-28): Again, a bit of a stretch. He hit .355 in 121 at-bats at age 25 with Cleveland and then hit .268/.368/.450 at 26 in 451 plate appearances. He posted a .396 OBP at 27, got traded to the Pirates and had a stretch of monster seasons from ages 28 through 32 -- and several more good ones after that.

Ben Zobrist (9.5 WAR at 27-28): We're getting further away from Donaldson's WAR -- Zobrist ranks 134th on the list of age 27-28 value -- but this is a pretty good match. Zobrist hit .200 in 80 games at ages 25-26 and then played well in a part-time role at 27. He had his big breakout season for the Rays at age 28 in 2009 and has averaged 5.8 WAR per season from 29 through 33.

So, in the past 60-plus years, there have been two really good comps for Donaldson: Martinez and Zobrist. One guy (Martinez) went on to have a Hall of Fame-caliber career and the other has been an extremely valuable player the past five seasons, probably the most underrated player in the game. I didn't find anyone who was a big star at 27-28 after having done nothing before that and then flamed out rather quickly. (Note: I'm not saying there haven't been excellent players who declined after 28, just no player who matches Donaldson's career arc.)

This suggests that Donaldson should once again be a potential MVP candidate for the Blue Jays in 2015 and remain a very good player into his early 30s.