The unsung star on each MLB playoff team

Alex Avila may not start but he could provide some pop for the Cubs late in games. Charles LeClaire/USA TODAY Sports

On July 25 of last season, the Cubs had the best record in baseball, and a massive lead in their division. Still, on that day, they paid a high price to acquire Aroldis Chapman. The idea wasn't so much to strengthen the Cubs for August and September; rather, they had October in mind, and Chapman did mostly hold up his end of the bargain. Chapman was known to be one of the most dominant relievers in modern baseball history, and without him, the 2016 Cubs might have reached a very different destination.

Five days before the Chapman blockbuster, the Cubs made a much lower-profile move to acquire Mike Montgomery. The idea was to use him as a swingman, and few imagined how brightly Montgomery's star would shine. Ultimately, Montgomery might have been more important to the Cubs in the playoffs than Chapman was. He emerged to be something of a secret weapon.

What is a secret weapon? Essentially, it's another way of calling someone underrated. And there's no real science to it, no falsifiability. It's a feel thing, but a team's secret weapon is its potentially most valuable player who many people would forget to include when rattling off the most valuable players. Like, Clayton Kershaw? Not a secret weapon. Brandon Morrow? More of a secret weapon. It's a hard thing to define, but you know one when you see one.

Herein, I'm identifying eight players. You might realize there are eight teams remaining alive in the playoffs. Not a coincidence! For each team, I've picked one player I think is most likely to serve as a secret weapon in October -- one guy I think should be good who it could be easy for the average fan to overlook. Here are some players with hidden values who could change the course of the month.

The teams are listed here alphabetically.

Arizona Diamondbacks -- Zack Godley, starting pitcher

You wouldn't question Zack Greinke's effectiveness, right? No, of course not. This year, Greinke allowed a .659 OPS. Godley allowed a .657 OPS.

I'm not trying to argue that Godley is every bit as dependable as Greinke is, but Godley reached 155 innings. It's not that small a sample. The key this year for Godley was polishing what might've become baseball's best curveball, and because of how the pitch moves, Godley was no less effective against lefties than he was against righties. Arizona might have some open questions in the bullpen, but the rotation is strong from front to back.

Boston Red Sox -- Christian Vazquez, catcher

The average catcher just posted a .725 OPS. Vazquez finished 10 points higher than that. Not bad for a defensive specialist, and Vazquez might've been powered along by a 13-point decrease in his rate of ground balls.

But here's the real thing: Reflect, again, on the defensive-specialist part. Baseball Prospectus tracks catcher defensive value, based on pitch framing, pitch blocking, and throwing. Vazquez just finished in fifth place, with positive marks across the board. Vazquez can block, throw, and frame, and now, for the first time, he can even help beside the plate, instead of only behind it. It has been a disappointing year for Red Sox position players, but Vazquez is a sneaky asset.

Chicago Cubs -- Alex Avila, catcher

Unless something goes horribly wrong, Avila won't be making regular starts. In October, he's going to be a backup catcher and a bench bat. Bench bats can do only so much, but Avila could be one of the more dangerous options that any manager has at his disposal.

My argument is both very complicated and wonderfully simple. Thanks to Baseball Savant, we have access to a stat called expected weighted on-base average. It's a measure of how well a player would have been expected to perform at the plate, given his walks, strikeouts and actual batted balls. We're talking launch angle and exit velocity and everything. Out of 301 hitters with at least 250 at-bats, Avila just ranked eighth best, between Nelson Cruz and Giancarlo Stanton. Avila could be good for a huge, late home run. He could be good for multiple.

Cleveland Indians -- Mike Clevinger, starting pitcher*

Clevinger is moving from the rotation* into the bullpen for the playoffs. The Indians' bullpen doesn't really need the help, but then, the rotation is also overflowing with riches. So Clevinger will serve as a possible multi-inning bullpen bridge.

Why is that exciting? Here's one reason: There were 134 pitchers who cleared 100 innings this season. Clevinger posted the sixth-lowest contact rate -- when batters attempted to swing, they made contact against Clevinger with relative infrequency. That was with Clevinger mostly starting. At the end of September, Clevinger relieved three times, and his fastball gained 1.4 miles per hour. That's extra gas, for a team with more than enough pitching already.

Houston Astros -- Brad Peacock, starting pitcher

It might feel like the Astros have some uncertainty behind Justin Verlander and Dallas Keuchel, what with Lance McCullers' recent DL stint and ineffectiveness. I'm sure they'd love to have McCullers at 100 percent, but don't sleep on the season that Peacock has had.

This year, 61 American League starting pitchers threw at least 100 innings, and Peacock ranked fifth in strikeout rate, between Chris Archer and Carlos Carrasco. Opponents slugged .322 against Peacock. If Peacock had a major problem, it was wearing down within starts, but over the first two times through the lineup, Peacock allowed a 2.05 ERA. Around the majors, only Kershaw was better.

With a deep bullpen, the Astros could look to Peacock to make four- or five-inning starts, and that could be all that they need.