Bargnani aggravated a strained left calf Wednesday night at Utah. He said this time it's more serious than when he first injured the calf and missed six games, all Raptors losses.
Bargnani is averaging 23.5 points.
He scored 36 points in a win over Phoenix on Tuesday night in his return from the six-game absence and had 25 points when he reinjured himself in overtime against the Jazz as he battled Paul Millsap for a rebound.
This marks Kleiza's first game in Denver since leaving the Nuggets two years ago to play in Greece. He was hurt last year when the Raptors played in Denver.