Each MLB playoff team's most important midseason acquisition for October

The field is set for the MLB postseason, and while most front offices have spent the past few years constructing their rosters to reach this point, some of October’s most impactful players could end up being those acquired this July or August.

Some contenders (Milwaukee) were more active than others (Colorado), but all have at least one piece that will be pivotal this month.  

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Astros: Roberto Osuna

It’s no secret that Osuna has plenty of off-the-field baggage, but his impact on the diamond has helped the Astros fill their most glaring need: a go-to closer in the ninth inning. Hector Rondon remained the closer after Osuna was acquired, but it didn’t take long for the former Blue Jay to claim the role. He has saved 12 games in as many chances, providing fewer near heart attacks than Ken Giles, Houston’s closer in 2017.

Red Sox: Ian Kinsler

Boston's biggest hole is bullpen depth to bridge the gap between their All-Star laden rotation and accomplished closer Craig Kimbrel. However, they made no such acquisition in July or August, but they did grab the veteran Kinsler, whose role is even more important with the season-ending injury to Dustin Pedroia. Kinsler is a .291 hitter in 134 career playoff at-bats, so he will add experience to a team that has not won a playoff series since 2013.

Indians: Brad Hand

You might be asking why not 2015 AL MVP Josh Donaldson? Well, Donaldson makes a deep offense even stronger, while Hand helps fill a role in the back end of an Indians bullpen that hasn’t been the same dominant force as in years past. Cody Allen is posting the lowest K/9 (10.7) and highest BB/9 (4.4) of his career, while Andrew Miller has missed time with injury and has his highest ERA (4.24) since 2011, his first season as a full-time reliever. Hand, meanwhile, is coming off his second straight All-Star appearance and has struck out 106 in 72 innings with a 3.20 FIP in 2018. He has shared the closer duties with Allen in Cleveland, converting eight saves and will almost certainly be pitching important late innings in the postseason.

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Athletics: Mike Fiers

A surprise contender, Oakland made a series of moves to boost its standing at the trade deadline, but its most important acquisition came in August. With the season-ending injury to Sean Manaea, Fiers will potentially start the American League wild-card game, and if he gets the nod, will play a major part in whether the team advances to a date with the Red Sox in the ALDS. He’s earned the spot, with a 2.90 ERA and a 2.0 BB/9 compared with a 8.9 K/9 in the nine starts he's made with Oakland.

Yankees: Luke Voit

Luke Voit? Who? Oh, just the guy who has averaged a home run every 9.4 at-bats since the Yankees acquired him for reliever Chasen Shreve in a late July trade that attracted little fanfare. Voit has set a career high in at-bats during his age-27 season, effectively stealing the first baseman job and relegating Greg Bird to bench duty. His 1.3 WAR since the trade to New York is the same as Bryce Harper’s total for the season.

Sudden bullpen troubles triggered by the injuries to relievers Brandon Morrow and Pedro Strop have thrust former afterthoughts like Chavez into pivotal bullpen roles. Chavez has been lights out since he was acquired from the Rangers in mid-July in a trade that, like Voit’s, received only minimal fanfare. In 37 innings on the North Side, he has a 1.15 ERA and has allowed only six H/9 and 1.2 BB/9. Strop’s status for the postseason is up in the air, and there is a legitimate chance that the Cubs will call on Chavez to get crucial outs in October.

The NL East champions made a few midseason acquisitions that haven’t panned out (Lucas Duda, Adam Duvall), but others, like Gausman, have been just what the doctor ordered. Always brimming with potential, the right-hander has been a huge help and appears destined to be in the postseason rotation. Since he was acquired, Gausman has allowed 4-plus earned runs just once in his 10 starts. As a bonus for the Braves, he doesn’t become a free agent until 2021.

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Dodgers: Manny Machado

With all due respect to the likes of John Axford and David Freese, who did you expect this to be? Machado was the crown jewel of the trade deadline and it took five Dodgers minor leaguers to acquire him from the Orioles. The four-time All-Star has slotted into the middle of the order, and although some of his numbers haven’t been as strong as in years past, he has still slugged .487 with 13 home runs in 66 games in his contract year.

Rockies: Seunghwan Oh

The Rockies didn’t do a ton of damage in the midseason trade market, but their one acquisition, Oh, has pitched close to expectations. In addition to helping shore up a disappointing bullpen, he has a 2.53 ERA and 1.03 WHIP. Like Hand and Chavez, he will be a bullpen fixture.

Brewers: Mike Moustakas

Not only is Moustakas an impact power hitter at the plate, but he brings experience from two extensive playoff runs with the Royals to a Brewers team that hasn’t played in the postseason since 2011. The owner of 66 home runs over the past two seasons, Moustakas is just another impact addition to a lineup that already has 30-home run hitters Christian Yelich, Jesus Aguilar and Travis Shaw. He hasn’t provided a ton of value defensively, but is a sure bet to be in the lineup for nearly every playoff game.