The 2017 MLB postseason was perhaps defined by Alex Bregman’s arrival. The third baseman saved his first career walk-off hit for Game 5 of the World Series – the momentous 10-inning romp that the Houston Astros won en route to the franchise’s first championship. Since then, the 24-year-old Bregman has fully bloomed, and will certainly garner MVP consideration behind Mookie Betts and Mike Trout.

While arrivals like these are not guaranteed – Bregman had pedigree and was the second overall pick back in 2015 – October heroics are a certainty. Let’s look at one player from each of the remaining eight playoff teams who could play an integral role in their club’s quest toward the Fall Classic.

Lance McCullers Jr., Astros

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As the Astros prepare to become the first team since the 1998-2000 Yankees to repeat as champs, the Houston bullpen is perhaps the weakest link on an impossibly deep team, which just added Lance McCullers Jr. at the end of September.

McCullers was sidelined in early August with a strained forearm, and the team was unwilling to stretch the young hurler out in time to start for the postseason. Of course, it helps when your rotation already consists of Justin Verlander, Gerrit Cole, Dallas Keuchel, and Charlie Morton, but McCullers coming out of the ‘pen could be deadly for opponents. Since returning in late September, McCullers has struck out four of the seven batters he’s faced. The 25-year-old right-hander isn’t unfamiliar with high-leverage relief tasks either, as McCullers earned a four-inning save in Game 7 of the ALCS last year, and played a key role in Game 7 of the World Series as well.

Christian Yelich, Brewers

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Picking the best player on the team to be an X-factor may seem like a cop out but, for the Brewers, how Christian Yelich performs will be a huge indicator of the club’s trajectory.

The presumptive NL MVP was baseball’s hottest player in the second half, and it wasn’t even close. Posting a .367/.449/.770 slash line with 25 home runs and 10 stolen bases, Yelich was worth 5.4 WAR by FanGraphs. The next best position player was Matt Chapman at 3.9 WAR. Yelich’s 220 wRC+ also led the entire MLB. The next closest was Justin Turner, a full 30 percentage points worse at 190 wRC+. By the end of the season, Yelich was the only player in the NL with an OPS of 1.000 or higher. Keeping him off base will be the most crucial task for the Rockies and whoever faces the Brewers next.

Walker Buehler, Dodgers

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If you were tuning into the NL Central tiebreaker and hadn’t followed the 2018 season, then you would have been forgiven for thinking Walker Buehler was a veteran ace of an incredible Dodgers staff, as the rookie threw five no-hit innings in the division-clinching victory.

With his first task handled with incredible ease, look for Los Angeles to continue to rely on the 24-year-old in must-win opportunities. Clayton Kershaw’s struggles in October are well documented at this point, despite flipping the script recently with a Game 1 win in last year’s World Series. But the Dodgers now have another bona fide ace to rely on if Dave Roberts has any hesitation of using the club’s presumptive No. 1.

Josh Donaldson, Indians

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There’s no getting around it: the postseason is the reason the Indians traded for Josh Donaldson.

After falling short of winning the World Series back in 2016, and being unable to make it past the first round last year, Cleveland had to do something. They added some ammunition to the bullpen to address some injuries with Brad Hand and Adam Cimber, but with breakout campaigns from Trevor Bauer and Mike Clevinger, and a healthy Carlos Carrasco, the lineup was the clearest weakness. That’s where Donaldson comes in. Beyond Jose Ramirez, Francisco Lindor, and Edwin Encarnacion, the bats lack some punch. If Donaldson can bring the rain, Cleveland could finally break their 70-year drought.

Mike Foltynewicz, Braves

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Tasked with facing Los Angeles at Dodger Stadium for Game 1 of the NLDS, Mike Foltynewicz will carry the heavy burden of being the most reliable starter in a surprise year for the Braves.

The tandem of Anibal Sanchez, Sean Newcomb, Julio Teheran, and late-season addition of Kevin Gausman were reliable enough to clinch the division, but all possess their own shortcomings. Sanchez was a reliable starter, but counting on the 34-year-old to continue his bounceback campaign in October seems foolhardy. In Newcomb’s first full season, the 25-year-old tapered off, continually battling control issues over the last two months. Conversely, Teheran seemed to figure it out late in the season, but still can’t recapture his 2013-14 prowess. No wonder this team was coy about committing to a starter beyond Foltynewicz in Game 1. If he can’t get the team off to a good start against a tough first-round opponent, the Braves playoff stay may be short.

Chris Sale, Red Sox

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With the 108-win Red Sox, the lineup is certainly potent and can go toe-to-toe with any playoff opponent. However, preventing other teams from scoring could be an obstacle, and that starts with the health of Chris Sale.

In his final start of the season, the left-hander’s velocity was down pretty sharply as Sale allowed three runs over 4 2/3 innings against the Baltimore Orioles. Even though manager Alex Cora asserts his ace is healthy, there is some worry that Sale’s shoulder injury that sidelined him in early September is still lingering. He will start Game 1 against the Yankees, and with David Price and Rick Porcello representing question marks of their own, Boston needs their ace to set the tone of the series.

Luke Voit, Yankees

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Since being acquired in July from the St. Louis Cardinals for reliever Chasen Shreve, all Luke Voit has done is slug.

In fact, over the final 30 days of the season, the 27-year-old Voit was far and away the best Yankees hitter. Across those 23 games, he owned a .337/.406/.744 slash line with 10 home runs, and his 207 wRC+ dwarfed Andrew McCutchen’s second-best mark of 154. Voit’s electrifying two-run triple against the A’s on Wednesday in the wild-card game was just his latest big hit. He may not be the sexiest name, but he could still be a key role player for a team loaded with sluggers.

German Marquez, Rockies

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Since the All-Star break, the only pitcher who has been worth more WAR than German Marquez was Jacob deGrom, per FanGraphs. With a 2.61 ERA and 2.25 FIP over the final 93 innings of his season, Marquez played a key role in getting the Rockies to this spot.

The 23-year-old came up short in the NL West tiebreaker against the Dodgers, and it was Kyle Freeland on short rest who shut down the Cubs in the wild-card game, but Marquez will need to make an impact in the division series for Colorado to advance. In order to do so, Marquez will have to reverse his previous fortunes against the Brewers, as the right-hander has a 5.40 ERA and 1.71 WHIP in two starts against Milwaukee this year.