This article is an extension of a comment I made here.
When looking at the title of this article, you thought two things.
The first is, "Who is Brayan Villarreal?"
Brayan Villarreal is a 25-year-old Tigers reliever in his second season with the club. In 54-and-two-thirds innings in 2012, he posted a 2.63 ERA with 66 strikeouts (10.9 per nine innings), nine holds and a .201 batting average surrendered. His ERA numbers were second-best among Tigers pitchers (just edging out Justin Verlander), and best among Tigers pitchers with at least 20 appearances.
The second is, "I don't remember Villarreal pitching for the Tigers in the World Series."
Well, that's just it. Villarreal hasn't played in the playoffs for the Tigers.
This is the result of Detroit's unconventional roster allocation. Detroit is only rolling with 11 pitchers, one fewer than a typical regular season, ALCS or World Series roster. Of those pitchers, six of them (Justin Verlander, Max Scherzer, Doug Fister, Anibal Sanchez, Drew Smyly and Rick Porcello) are primarily starts. That leaves Detroit with only five relievers, one or two fewer than a team typically has.
And when one of those five relievers is Jose Valverde, who is averaging a 30.38 ERA while giving up nine earned runs and two homers in just two-and-two-thirds innings, expect problems.
This has forced the Tigers to juggle their pitchers, often placing them in unfamiliar roles. Porcello and Smyly have both appeared in relief, and Phil Coke has taken the closer's mantle. Joaquin Benoit and Octavio Dotel have each appeared in almost half of the Tiger's eleven playoff games, often in situations they were unfamiliar with.
This situation could have been ameliorated if Porcello or a batter had been left off the playoff roster in favor of Villarreal.
The dearth of relievers seems preposterous when you consider that the success of 2011's World Series teams (the Rangers and Cardinals) were due in large part to solid middle relievers such as Alexi Ogando, Mike Adams, Arthur Rhodes and ironically, Dotel, who is now with the Tigers.
So why wasn't Brayan Villarreal put on the playoff roster?
One reason might have been that he's only 25. Then again, Porcello is 23. So is Smyly, who is a rookie to boot (albeit he likely made the roster due to other factors, such as his handedness). Reliever Al Alburquerque is one year older than Villarreal, but the surprise in his making the playoff roster is that he was sidelined most of 2012 with injury, playing in only eight big-league games.
Another reason might be his unfavorable second-half split. Villarreal posted a 3.86 ERA since the All-Star break. While that's not that good, it's still a run-and-a-half better per nine than the second-half stats of Benoit or Coke. Again, that is not really a reason if you look at the stats.
So, there really wasn't a good reason to leave Villarreal off the playoff roster.
Bottom line: Leaving one of the better relievers in Villarreal at home means equals the San Francisco Giants with their second World Series.