Parker has been rehabbing strenuously to try to recover from a slight hamstring strain he suffered in Game 3. On Saturday, Parker told reporters his hamstring "could tear any time now."
Parker struggled in the second half of Game 4 as the Heat pulled away to even the series 2-2.
After Boris Diaw started the second half of Game 4, Gregg Popovich said Sunday the plan is to keep the usual starting five (Parker, Danny Green, Kawhi Leonard, Tim Duncan, and Tiago Splitter) for Game 5 -- but that "could change." Popovich pulled Splitter 45 seconds into Game 4 as the young center had a turnover and was burned badly when matched up with guard Dwyane Wade (for some ungodly reason).
Diaw is thought to provide the Spurs with more versatility and a better chance at matching the Heat's succesful "small-ball" lineup they shifted to in Game 4 featuring Mike Miller in the starting lineup instead of Udonis Haslem.
Game 5 is at 8 p.m. ET Sunday.