(Reuters) - The Chicago Cubs were given a welcome slugging boost on Tuesday when Kyle Schwarber was added to their World Series roster hours before the scheduled start of Game One versus the host Cleveland Indians.

Schwarber, who has spent the year recovering from a knee injury he suffered in the third game of the season, could be used as a designated hitter by the Cubs, who have gone 108 years without a World Series title.

To make room for Schwarber, Chicago removed relief pitcher Rob Zastryzny from their playoff roster.

"He's been doing everything, he's swinging the bat well," Cubs manager Joe Maddon told reporters about Schwarber, who was given the all-clear by his orthopedic surgeon to prove his fitness in the Arizona Fall League on Saturday and Monday.

"He's running really well, actually. He's done some sliding drills, all that kind of stuff to just test the whole thing out. He's given us another option to think about."

Schwarber tore the anterior and lateral collateral ligaments in his left knee on April 7 in a freak collision with team mate Dexter Fowler during a game against the Arizona Diamondbacks. He has since been working hard on rehabilitation.

The 23-year-old slugger, who set a Cubs postseason record with five home runs in 2015, would give his team a potent left-handed bat as a designated hitter.

(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)