7:03 PM ET
Irving is sidelined with flu-like symptoms, and Horford is getting the evening off to rest.
Horford missed seven games in December with left knee soreness.
Celtics coach Brad Stevens said Terry Rozier will take Irving's spot in the starting lineup and Aron Baynes will fill in for Horford.
Boston enters Wednesday's contest with a four-game winning streak.
The Cavaliers have lost 16 of their past 17 and have the NBA's worst record at 9-39.
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