MLB playoffs: Why Clayton Kershaw, Luis Gil, Cade Horton, more players were left off Wild Card Series rosters

Major League Baseball's postseason got underway on Tuesday with Game 1 of each of the four Wild Card Series. The winners of these three-game sets will then advance to MLB's more traditional playoff structure, beginning with the best-of-five divisional round.

The start of the postseason also means that the involved teams have to announce their rosters for the round. Unlike during the regular season, when teams are allowed to make transactions at their discretion, playoff rosters are treated with more rigidity. Teams can only replace players mid-series in the event of an injury, and anyone removed during a series must sit out the subsequent round too.

MLB playoff predictions: Expert picks for Yankees vs. Red Sox, Cubs vs. Padres and every Wild Card Series

Kate Feldman

In other words, clubs have to be deliberate with who they do and to not roster, leading to some situations where notable players are excluded. Below, CBS Sports has put together a list of recognizable players who did not make their team's Wild Card Series roster for this or that reason. In some cases, it's because of health; in others, it's because of strategy. 

Either way, this should answer why certain players aren't around.

1. Clayton Kershaw, LHP, Los Angeles Dodgers

Kershaw, who recently announced his intention to retire this offseason, may have already thrown his final pitch. He started Sunday's season finale against the Mariners, delivering 5 ⅓ shutout innings on 94 pitches. That appearance meant Kershaw would not be available to pitch this round on normal rest. He wasn't going to be part of the postseason rotation regardless, but the Dodgers are likely to add him to their bullpen if they're able to defeat the Reds and advance.

2. Lucas Giolito, RHP, Boston Red Sox

Giolito finished third on the Red Sox in starts and innings pitched, but he won't be taking the mound at any point this series against the Yankees. Rather, the Red Sox ruled him out on Monday, disclosing that he was dealing with elbow discomfort. The Red Sox will turn to Garrett Crochet and Brayan Bello in Games 1 and 2. Giolito's likely Game 3 start, should the series require it, will presumably be given to rookie lefty Connelly Early, one of CBS Sports' top breakout candidates.

3. Cade Horton, RHP, Chicago Cubs

Coming into the season's final fortnight, Horton was a lock to start Game 1 or 2 for the Cubs. Unfortunately, at some point along the way, he fractured a rib. Horton won't be available at all this series, and it's to be determined if he can factor into the divisional round should the Cubs advance. Chicago will turn to Matthew Boyd and Shota Imanaga in Games 1 and 2, with a potential Game 3 starter to be determined from a candidate pool that includes Jameson Taillon and Colin Rea.

4. Emmanuel Clase, RHP, Cleveland Guardians

If you haven't been paying attention over the last few months, then you may not realize that Clase hasn't pitched since July 26. Why? Major League Baseball placed him on administrative leave while they investigate potential misconduct related to gambling. Clase is one of two Guardians pitchers who were placed on administrative leave during the summer, with the other being right-handed starter Luis L. Ortiz. The Guardians have largely used Cade Smith in save situations.

5. Luis Gil, RHP, New York Yankees

Gil, last year's American League Rookie of the Year Award winner, started Sunday's season finale as part of the Yankees' efforts to win the AL East and earn a first-round bye. As such, he won't be available on normal rest until the divisional round, should the Yankees prevail over the Red Sox. New York will instead turn to Max Fried, Carlos Rodón, and Cam Schlittler as their starters.