The Blue Jays spent the final two months of the 2017 season buried in the depths of the American League Wild Card race. Following back-to-back AL Championship Series appearances, Toronto finished 76-86, nine games out of the second Wild Card berth.
Meanwhile, Giancarlo Stanton chased 60 home runs, and other star sluggers, such as Aaron Judge and J.D. Martinez, rode blistering hot streaks to the finish line for playoff-bound clubs.
All of that might have obscured another development, which was that Josh Donaldson staked a credible claim as the best hitter in baseball over those final two months.
Donaldson's renaissance -- following a relatively brief rough patch -- sets both him and the Blue Jays up well for 2018. After holding on to Donaldson amid swirling trade rumors, Toronto can try to ride its All-Star third baseman and a tweaked roster back to the postseason. For his part, Donaldson has a chance to soar into free agency on a high note, barring an agreement on a contract extension prior to next winter.
Donaldson performing at an elite level isn't a new phenomenon. Since his late-blooming breakout for the A's in 2013, only Michael Trout has accrued more value, according to FanGraphs' Wins Above Replacement, with Paul Goldschmidt a distant third.
During that time, Donaldson won the 2015 AL Most Valuable Player Award and finished in the top five twice more by playing stellar defense at the hot corner and batting .282/.377/.524 over the past five seasons. His 164 home runs rank sixth in the Majors over that stretch, while his 147 weighted runs created-plus (wRC+) is tied for fifth.

But Donaldson's 2017 was full of early frustrations. Right calf issues dogged him throughout Spring Training and put him on the disabled list on April 14. He didn't return until May 26, and while he performed well initially, he then posted a meager .184/.327/.272 line over a 38-game stretch from June 14-July 29. Despite homering on the final day of July, Donaldson entered August with an .807 OPS and 117 wRC+ -- decent numbers, but far below his standard.
Then, from Aug. 1 onward, Donaldson returned to being a destructive force at the plate.
Donaldson's .302/.410/.698 slash line equated to a 187 wRC+ that ranked first among the 211 batters who had at least 150 plate appearances over the final two months -- ahead of even Stanton and Martinez (both 177). Donaldson's 22 home runs ranked behind only those two sluggers, and his total included five multihomer games.

The Statcast™ numbers back up this hot streak, as Donaldson ranked a close third to Judge and Martinez with a .431 expected weighted on-base average (xwOBA), a metric that factors in a hitter's quality of contact, in addition to his strikeouts and walks.
Among more than 200 players who put at least 100 balls in play from Aug. 1 on, Donaldson also ranked in the top five in average exit velocity (91.1 mph), hard-hit rate (49 percent) and barrel rate (18.4 percent). His improvement in each of those categories compared with the first four months of the season was considerable, especially in hard-hit rate, which measures how often a batter achieves an exit velocity of 95 mph or higher.
Largest increase in hard-hit rate
Aug.-Oct. vs. April-July (Minimum 100 batted balls in each *)

1. Kevin Kiermaier: +17.8 percentage points (to 42 percent)
   
2. Carlos Gonzalez: +15.4 percentage points (to 46.7 percent)
   3. Josh Donaldson: +12.5 percentage points (to 49 percent)
   
3. Xander Bogaerts: +10.3 percentage points (to 37.3 percent)
   
4. Mitch Haniger: +8.3 percentage points (to 39.7 percent)
   * 188 qualified hitters
   Where did that increase come from? Through the first four months, Donaldson simply wasn't punishing pitches in the upper two-thirds of the strike zone, with a hard-hit rate (40.6 percent) barely above the AL average (39.5 percent). Afterward, his 63.2 percent hard-hit rate on those offerings trailed only Judge.

The peak of Donaldson's hot streak came at Target Field from Sept. 14-17, when he went 10-for-17 with five home runs and seven RBIs. In the final game of the series, the Twins' Kyle Gibson delivered a fastball over the heart of the plate in the first inning, and Donaldson pummeled it into the upper deck. With a 113.5-mph exit velocity and projected distance of 481 feet, it was Donaldson's hardest homer, and tied for his longest, since Statcast™ debuted in 2015.

Donaldson turned 32 in December, and while he was an iron man from 2013-16 -- playing at least 155 games each season -- last year's injury issues can't be ignored. There is certainly some risk here.
However, if Donaldson's late-2017 rampage is any indication of where his '18 campaign is headed, it would go a long way toward making Toronto's postseason absence a short one.