ST. LOUIS -- Once the Cubs return home on Friday, manager Joe Maddon will likely have lots of stats to study to help determine the 25-man playoff roster for the National League Division Series presented by T-Mobile.
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The Cubs don't have to make a final decision until before Game 1 of the NLDS on Oct. 6 against the Nationals in Washington. That's a lot of time for the so-called "geeks" in the baseball-operations department. Maddon's toughest picks will be who's in, and who's not in the starting rotation.
Top 5 roster decisions
Who starts?
Last year, the Cubs relied on four starters and they will likely do the same this postseason. The key pitcher is whoever starts Game 1, because he also could start a deciding Game 5. Jonathan Lester and Kyle Hendricks are in, and Jacob Arrieta should be but he's not 100 percent recovered from his right hamstring injury. Do the Cubs decide to give Arrieta more time and go with John Lackey, who was solid in the clinching game Wednesday against the Cardinals? Or do they pick Jose Quintana? Lackey was roughed up at Wrigley by the Nats on June 28, giving up eight runs on nine hits, including three homers, over 5 1/3 innings. Quintana has never faced them but the Nationals are second in the NL in batting average against lefties.
Who's in the bullpen?
The Cubs carried 11 pitchers in the postseason last year, which would mean seven relievers. Wade Davis, Pedro Strop, Hector Rondon, C.J. Edwards, Brian Duensing and Mike Montgomery are set. If they want another lefty, Justin Wilson could be added. Wilson had a solid outing Saturday against the Brewers but then struggled to throw strikes against the Cardinals on Tuesday. Another option would be to have whoever isn't in the rotation among the starters shift to the bullpen. Lackey did that last year.

Who's on the bench?
The Cubs have plenty of movable parts. If Maddon decides to start Javier Baez at second, that would likely put Benjamin Zobrist either in the outfield or on the bench. Having a super-utility player like that handy -- who also was the 2016 World Series MVP -- can help a manager when he makes double-switches. Thomas La Stella is a solid left-handed bat, and rookie Ian Happ, a switch-hitter, is a mini-Zobrist who can play all outfield positions and second base. Albert Almora Jr. has been the No. 1 bat off the bench against lefties and is solid defensively. Outfielder Leonys Martin, a left-handed hitter, may be an option as a defensive sub.
Who's in left field?
This is more of a lineup decision than roster decision, but Maddon has said the toughest spot to fill on his card is left field. The choices include Zobrist, Happ and Kyle Schwarber. Schwarber had the most success against the Nats this season, batting .286 with one homer and one double. Zobrist only played two games against them because of injuries and was 1-for-6, and Happ was 4-for-23. Defensively, Happ is the most athletic.

Who's the backup catcher?
Willson Contreras has survived a hamstring injury that sidelined him for a week and taken several foul balls off his body. He provided the spark in the second half, batting .311 with 10 home runs and 29 RBIs in 23 games from July 14-Aug. 9. Who will the Cubs pick between Alex Avila and Rene Rivera? Avila is a left-handed hitter, Rivera is right-handed. Rivera has had more success offensively since joining the Cubs. Both are good defensively. The Cubs do like having a veteran catcher matched up with Lackey, and Rivera caught the right-hander on Wednesday against the Cardinals.