Biggest X-factors heading into the MLB postseason

We look for baseball's biggest stars to make big contributions in the playoffs, but often it's the secondary players that make the biggest difference. Here's a look at 25 X-factors going into the postseason.

Shane Bieber, SP, Indians

Trevor Bauer is back, but without working up his stamina, Bieber should still play a key role for Cleveland. The rookie produced a 4.55 ERA during the regular season, but that's deceiving given his 3.23 FIP and amazing 5.13 K/BB ratio. During his three-year minor league career, Bieber produced an outstanding 2.24 ERA with only 19 walks in 277 innings. His future is extremely bright, but he could become known sooner than later as either the team's fourth starter or long inning reliever in the playoffs.

Ryan Brasier, RP, Red Sox

Boston has plenty of arms that get more press, but Brasier has arguably been the team's best reliever during the second half of the season. Promoted in early July, Brasier allowed a run in only six of his first 33 appearances with a 1.7 BB/9. After spending 2017 in Japan, Brasier has figured out how to get outs in the majors, following a minor league season with similar success. Manager Alex Cora has used Brasier as a key setup man over the last two months, and that will likely continue into the playoffs.

Zach Britton, RP, Yankees

Baltimore's former All-Star got off to a late start this season and still hasn't missed bats like we saw during his two All-Star campaigns in 2015 and 2016. Still, Britton has been effective since joining the Yankees in July and has a ridiculous 73 percent groundball rate. That's key pitching at Yankee Stadium and getting critical outs against the likes of Khris Davis, Mookie Betts, and J.D. Martinez in the playoffs.

Jesse Chavez, RP, Cubs

An under the radar addition from Texas in mid-July, Chavez has arguably been his team's best reliever over the last two-plus months. The right-hander had a 1.29 ERA and 38/5 K/BB in his first 35 innings, playing a key setup role for the Cubs with Brandon Morrow and Pedro Strop injured. Aiding a bullpen that has been in relative shambles due to injuries, Chavez will almost certainly seen some critical innings during October.

Charlie Culberson, SS, Braves

Atlanta shortstop Dansby Swanson suffered a torn ligament in his hand during the last week of the season, so the Braves could rely on Culberson during October. If nothing else, Culberson is experienced. The 29-year-old made appearances in the playoffs with the Dodgers over the last two years and got his fair share of playing time Corey Seager's stead last year, going 8-for-16 at the plate. He's produced an OPS above .800 for the Braves this year after coming over in the Matt Kemp trade, and there's an argument to be made that he's actually an offensive upgrade over Swanson.

Yandy Diaz, 3B, Indians

Cleveland was hoping Diaz would develop power in the minors this year, but his bat is helpful anyway. A highly disciplined hitter, Diaz's on-base percentage has hovered around .350 in the majors since he was initially promoted last year. He also shows a solid glove at the infield corners, and could be a viable fallback option if Josh Donaldson's calf injury acts up again.

Nathan Eovaldi, P, Red Sox

Which Eovaldi will Boston be getting in October? Overall, his numbers have been excellent since being acquired from Tampa Bay at the trade deadline, with a 3.46 ERA and 44/12 K/BB in 52 innings. However, it's worth noting that Eovaldi was bombed in five of his 11 appearances. He's coming off two outstanding starts, and could play a key role if Chris Sale's shoulder isn't back to normal.

Dylan Floro, RP, Dodgers

The Dodgers added Floro from Cincinnati in early July, and he's been their most effective reliever during that time. Over his first 29 appearances, he posted a 1.63 ERA and 1.05 WHIP with a 10.1 K/9. Kenley Jansen had another very good year, but he's had some issues with consistency. Floro's increased velocity and groundball rate this season make him a potential alternative.

David Freese, 3B/1B, Dodgers

Dodgers fans have been treated to Freese's hot bat in September, as he's posted an OPS better than 1.100 as a platoon player in September. Freese has really done well in the role between Pittsburgh and LA this season, and his playoff track record is impeccable, as Cardinals fans can attest. Including his time as the 2011 World Series hero, Freese is a career .282/.357/.517 hitter during the playoffs in nearly 200 plate appearances.

Marwin Gonzalez, SS/OF, Astros

Carlos Correa has had an injury-plagued year and has been truly awful at the plate since the break, with a sub-.500 OPS. He hasn't been doing himself or the Astros any favors by trying to play hurt, but Gonzalez is a great alternative. After a slow start, he's produced an .872 OPS through 53 games in the second half. As much as Correa did for the team in 2017, the Astros are better off with Gonzalez as their starting shortstop in October.

Curtis Granderson, OF, Brewers

Granderson is in the twilight of his career and will get another shot in the playoffs this year with Milwaukee. Still a capable corner outfielder, Granderson has produced an OPS above .800 since joining the Brewers and has hit nine home runs in 237 career playoff plate appearances. At worst, he will be used as a key pinch-hitter in October.

Enrique Hernandez, UT, Dodgers

Even on a team loaded with depth, Hernandez continued to carve out a prominent role with the Dodgers in 2018. The utilityman nearly doubled his career home run output this season and has an .836 OPS vs. lefties during his career. The additions of Manny Machado and Brian Dozier improved the team's lineup against southpaws, but Hernandez also remains a key hitter in that area.

Matt Holliday, 1B/OF, Rockies

After sitting out the first four months of the season, Holliday hooked on with the team that drafted him and has been tremendous since being promoted in August. The seven-time All-Star produced an .855 OPS through his first 52 plate appearances, becoming a great contributor vs. lefties. His playoff experience should also come into play for a relatively inexperienced team, with 73 playoff games under his belt.

Corey Knebel, RP, Brewers

An All-Star last season, Knebel suffered a hamstring injury early in the year and had a rough time getting on track. It's far to say he's been on point in September, throwing 13 straight scoreless appearances with 26/3 K/BB in 13.1 innings. He's shared closer duties with Jeremy Jeffress in Milwaukee's quietly elite bullpen, and will play a key role in October.

Tommy La Stella, IF, Cubs

Chicago's middle infielder depth was greatly hindered with Addison Russell's disturbing off-field situation, putting pressure on the team's bench. One of their key bench players has been pinch-hitter extraordinaire Tommy La Stella, who has appeared in more than 100 games this year but started less than a quarter of them. He's hit above .300 as a pinch-hitter this season, but there's a possibility he will be pressed into more action in October if the Cubs suffer an injury.

Ramon Laureano, OF, Athletics

Promoted in early August, Laureano has been a revelation both at the plate and in the field for Oakland. After producing a .905 OPS at Triple-A Nashville, Laureano has hit nearly as well in Oakland while also swiping seven bases through 45 games. After trying several other options, the A's have finally found their center fielder of the future and right now. His athletic ability should make a huge impact in October.

Kenta Maeda, RP, Dodgers

Maeda moved to the bullpen and played a key role in the playoffs for LA last year, and he's set to do the same in 2018 after making 20 starts. Last year he allowed just one run in nine appearances during the playoffs, and with Kenley Jansen's inconsistency, Maeda will continue to serve as an important fallback plan.

Adam Ottavino, RP, Rockies

The Rockies made drastic offseason moves to fix their bullpen, but their best option was already on the team. Ottavino has been of baseball's elite relievers this season, with a 2.26 ERA and 108 strikeouts through 75.2 innings. While Wade Davis remains the closer, Ottavino is the key bridge for the team due to the struggles of Bryan Shaw and Jake McGee.

Steve Pearce, 1B, Red Sox

Pearce was acquired from Toronto in late June, and he's been a savior with Mitch Moreland's second half struggles at the plate. Through 49 games with Boston, Pearce produced an .882 OPS with an on-base percentage near .400. His ability to punish lefties, in particular, could be key for the Red Sox in the playoffs.

Oliver Perez, RP, Indians

Andrew Miller was Cleveland's clear top lefty in the pen entering the year, but his injury issues forced the Indians to improvise. Perez has come up big as one of the top lefty specialists in MLB, with a 1.42 ERA and 43/7 K/BB through 31.2 innings. If Miller continues to struggle like he did in September, Perez's role will be even more important.

Ryan Pressly, RP, Astros

Among reliever acquisitions, Roberto Osuna got most of the press for Houston, but Pressly has been their most successful addition. He's been almost untouchable since Houston acquired him from Minnesota, allowing just two runs in 22.1 innings with 30/2 K/BB with the team. Pressly should continue to be a key bridge in a dominant bullpen.

Blake Swihart, C, Red Sox

There's no debate Swihart has been a relative bust as a former top prospect. That said, he's had a solid second half for Boston with a .741 OPS in 99 plate appearances, and he's been the team's best hitting option behind the plate. While Christian Vazquez's defense has been instrumental in the pitching staff's success, Swihart is capable if and when the Red Sox need late offense.

Touki Toussaint, P, Braves

Toussaint's role remains to be seen, but he's a potential difference maker in any role due to his biting curveball. The 22-year-old pitched well late in the year despite mediocre control and was dominant in the minors, posting a 2.38 ERA and 163 strikeouts in 136.1 innings between Double- and Triple-A. Still in his first time around the league, unfamiliar hitters won't want to see his great stuff.

Framber Valdez, P, Astros

Valdez has a chance to be Houston's fourth starter in the playoffs if Charlie Morton's shoulder injury is worse than the Astros think. Even if he has to move to the bullpen, Valdez is clearly a nice weapon after posting a 71 percent groundball rate in the majors. Even with his struggles avoiding walks, the rookie's ERA hovered near 2.00 in the majors.

Luke Voit, 1B, Yankees

Yankees GM Brian Cashman could earn Executive of the Year for his Voit trade alone. Stuck at Triple-A in the Cardinals system, Voit was traded to the Yankees at the deadline and has been a revelation. Through 36 games, he's hit 11 home runs with an OPS above 1.000. The Yankees hoped to get a boost from Greg Bird's return from injury, but his opportunities have been few in September due to Voit's amazing play. The late-season power is far more than what we saw of Voit in the minors, but he still hit above .300 over the last two years.