Foster missed practice for a third consecutive day Friday with an injured hamstring, but Kubiak said that the NFL's leading rusher from last season "took a big step forward" in his rehabilitation and will be a game-time decision. Foster is officially listed as questionable for the game.
"I feel better than yesterday," Foster told reporters Friday. "It's just, like we said, it's one of those game-time decisions, so we'll just have to wait and see."
Kubiak told reporters that Derrick Ward will start if Foster is ruled out, with Ben Tate serving as the backup. Ward and Tate have seen most of the work during practice this week.
Asked to describe his side workout during Friday's practice, Foster told reporters, "I strided today ... I didn't frolic," making light of his comments Wednesday, when he described himself as "running, cutting and frolicking," per ProFootballTalk.com.
"We're gonna wait and see how I feel tomorrow," Foster said. "... If you rush a hamstring, it's gonna bite you again."
Kubiak complimented Ward's downhill running style and Tate's speed Friday, but it's clear the coach wants his star back in the fold as soon as possible.
"We need to be at our best as a football team to win this game, and (Foster) puts us at our best," Kubiak said Thursday. "But at the same time, if he can't go, if the trainers say that 'No, he can't go or it's not smart,' then we have to listen to them."
Foster had a career day against Indianapolis in last season's opener -- with a franchise single-game-record 231 rushing yards and three touchdowns.
Beyond Foster's status, Kubiak said his squad is itching to face Indianapolis.
"They're tired of practicing," he said. "They're excited to go out there and see where they're at."
The Associated Press contributed to this report.