Josh Donaldson, one of the best two-way players in baseball, has been dealt to Toronto.

With 15.4 WAR in 2013-14 (second to Mike Trout), Donaldson ties Chuck Knoblauch for the most age 27-28 WAR of any player who changed teams going into or during age 29. Even if you don’t buy his top-notch defensive metrics, Donaldson ranked 6th in offensive WAR for the last two years. He’s a player.

Ninety-one modern players tallied 12+ WAR for age 27-28. Here are the 11 who changed teams going into or during age 29, with their WAR totals for 27-28, and then 29-30 and 29-32. The rankings are among MLB position players during the years the player was in a certain age group; they are not age-group rankings.

* Mize played at 29, then missed age 30-32 in the service and returned at 33. The totals and rankings shown in his “29-30” and “29-32” columns simply skip the missed years, and so cover 1942/’46 and 1942/’46-48. No one else on this list missed a full year during age 27-32.

If we don’t count my fudged rankings for Mize, none of the others ranked in MLB’s top 15 during the years they were age 29-30 or 29-32. But that’s a different topic.

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Besides Knoblauch and Donaldson, ten other players changed teams after logging 15 WAR in any two-year span:

• Rogers Hornsby — 18.9 WAR, age 31-32, 3rd in MLB for 1927-28. Dealt for players and $200,000. Gave the Cubs one more MVP year at 33, but was rarely healthy after that. All you need to know about The Rajah’s personality: Traded three years in a row, each time carrying a 2-year total of at least 14.5 WAR.
• Eddie Collins — 18.1 WAR, age 26-27, 2nd in MLB for 1913-14. Connie Mack sold the reigning MVP for $50,000 due to salary inflation caused by the Federal League and by four pennants in five years. Collins remained a superstar for many years, ranking 5th in total WAR for the 10 years after the sale.
• Babe Ruth — 17.6 WAR, age 23-24 (14.5 as a player, 1st in MLB for 1918-19, and 3.1 as a pitcher). Sold for $100,000. Did all right afterwards.
• Jimmie Foxx — 17.3 WAR, age 26-27, 2nd in MLB for 1934-35. Dealt for players and $150,000. Foxx had six more good years with Boston, but never reached his 8.1 WAR average for seven full years in Philly. (The dispersal of Mack’s second dynasty was slower than the first. Al Simmons was moved after 1932’s distant 2nd-place finish; Lefty Grove, Mickey Cochrane and Maxie Bishop followed after ’33. But Mack kept Foxx until the A’s finally hit the cellar in ’35.)
• Alex Rodriguez — 15.1 WAR, age 23-24, and 17.2 WAR, age 26-27, both 2nd in MLB, for 1999-2000 and for 2002-03. Left Seattle as a free agent, then dealt to the Yankees after three MVP-caliber years in Texas. Remained a top player for five years in the Bronx (two MPVs, 2nd in total WAR) before age and injury took hold.
• Tris Speaker — 17.0 WAR, age 26-27, 2nd in MLB for 1914-15. Traded for players and $55,000 after his second title year with Boston, when he wouldn’t take a big salary cut. (Player pay fell sharply when the Feds folded.) Third in total WAR for his seven years as a BoSox starter (after Collins and Cobb), and third for the 10 years after the trade (trailing Hornsby and Ruth).
• Barry Bonds — 16.9 WAR, age 26-27, 1st in MLB for 1991-92. Left Pittsburgh as a free agent after his 2nd MVP in three years. Bonds won five more such crowns with the Giants, not without some growing pains. (Barry’s 84.1 WAR for age 24-33 — presumably “clean,” although who really knows — rate 5th all-time.)
• Jason Giambi — 16.9 WAR, age 29-30, 3rd in MLB for 2000-01. If you can’t beat ’em, join ’em. Giambi had one top-flight year with the Yanks, but the title still eludes him.
• Robinson Cano — 16.0 WAR, age 29-30, 2nd in MLB for 2012-13. Trying a new tack, New York let a perennial MVP candidate get away over bushels of money.
• Home Run Baker — 15.2 WAR, age 27-28, 3rd in MLB for 1913-14. Sat out all of 1915 in a salary fight. Finally sold for $37,500 to the Yanks, where he had four good years (11th in total WAR for 1916-19) but never approached his A’s peak.

Including Donaldson and Knoblauch, all 12 of these players ranked 3rd or better in total WAR for the prior two years.

The 12 prior transfers of these 15-WAR players were all centered on money. The only player going the other way in these deals who totaled 15 WAR afterward was Sad Sam Jones (in the Speaker deal), with 40 WAR over 20 years. Players at this level don’t get put into challenge trades.

But Donaldson is still cheap, expected to earn less than $5 million in 2015, his first year of arbitration eligibility. Billy Beane has a tight budget, but he’s not dealing a top player just to save $5 million. He must think this will make the A’s better at least by 2016, and for years after that.

Could that reflect Bean’s private view of Donaldson, or of late-bloomers in general? Donaldson’s sudden emergence at age 27 was very unusual. He had just a half-year’s experience in MLB, and a so-so career in the minors. Two related measures reflect this rarity:

(1) Out of 98 players whose age 27 yielded either 7+ WAR or 6+ offensive WAR, only Ichiro Suzuki and Jose Abreu were less established through age 26 than Donaldson, and that was only because they had yet to sign with a big-league team. Three others had less than 1,000 PAs through age 26, but all were regulars at 26:

• Josh Hamilton debuted at 26 (after a self-inflicted delay) with a 131 OPS+ in 337 PAs.
• Matt Carpenter got his first steady gig at 26 with a 125 OPS+ in 340 PAs.
• Jim Gentile broke through at 26 with a 145 OPS+ in 464 PAs.

Donaldson’s half-year at age 26 brought a mere 91 OPS+. And all three above had better bush-league numbers.

(2) Out of 91 players who totaled 12+ WAR for age 27-28, only Donaldson was not a regular by age 26. All but John Valentin had over 1,000 PAs by age 26, and Valentin at 26 played 144 games and logged 5.2 WAR.

So in this sense, Donaldson is unique in modern baseball. And although he was a late-1st-round pick at age 21, his minor-league record is spotty. His two good offensive years were both about 50 games — his pro debut, at the lowest levels, and then his third turn at triple-A.

It’s well established that players who break through in their late 20s tend to have shorter peaks. Donaldson’s second big year tends to mitigate that factor, but Beane still might be playing those percentages.

What do you think? Will Donaldson be a long-term star for the Blue Jays? Did the A’s get enough in return?