Major League Baseball's postseason will get underway this afternoon with the American League side of the bracket kicking off play. That means, among other things, that teams are finalizing their playoff rosters. It's to be seen what that means on the National League side, but a few AL clubs made the surprising decision to add rookies to their initial Wild Card Series roster. Or, in other words, a couple of players will be making their big-league debuts in the playoffs.

The most notable of these cases belongs to the Minnesota Twins, who promoted outfielder slash first baseman Alex Kirilloff, according to's Jonathan Mayo. Kirilloff, 23 come November, batted .283/.343/.413 with nine home runs in 94 Double-A games last season. He was ranked by CBS Sports as the best prospect in the system entering the offseason:

Kirilloff has an unorthodox swing, as he's prone to stepping in the bucket -- or striding away from the plate. This is often frowned upon, since it theoretically makes it tougher to hit outside pitches, but some batters -- e.g. Khris Davis -- have made it work. Kirilloff might be the next thanks to his feel for hitting and the natural loft in his swing.

Provided Kirilloff keeps hitting, the development worth watching here is where the Twins stick him defensively. They've had him crosstrain between first base and the corner outfield, and it's possible that he could ping pong back and forth as needed, giving him a little additional value.

Kirilloff's placement on the roster likely means that either outfielder Byron Buxton (concussion-like symptoms) or third baseman Josh Donaldson (calf) will miss Minnesota's series against the Houston Astros. Manager Rocco Baldelli could resort to using Marwin Gonzalez at third or Jake Cave in center, depending on which one is absent. 

The Astros, for their part, are rostering outfielder Chas McCormick. He hit .262/.347/.466 in Triple-A last season, and profiles as a tweener type thanks to a tool box full of average grades.

Elsewhere, the Rays have opted to carry 23-year-old left-handed pitcher Shane McClanahan for their series against the Toronto Blue Jays, according to Marc Topkin of the Tampa Bay Times.

McClanahan,  the 31st pick in the 2018 draft, appeared in just four games above High-A in 2019. He has a good fastball-breaking ball combination, though evaluators are split on if he'll be a starter or reliever for the long haul. He's expected to work out of Tampa Bay's bullpen for now.