The team said Thursday that Warren has plantar fasciitis in his right foot and will be listed as week to week. It's the same injury that kept All-Star forward Domantas Sabonis from returning to action in the NBA's bubble in August.
Indiana also will be without backup guard Brian Bowen II for 6-8 weeks because of a partially torn groin muscle.
Warren's injury could be more detrimental. Last season, he scored 19.8 points while shooting 53.6% from the field -- both career highs. And in the bubble, Warren was spectacular, averaging 31.0 points in six games, including a 53-point game against Philadelphia that tied the team's single-game scoring record.
"He's just a sneaky scorer, and we've got to take advantage of that," president of basketball operations Kevin Pritchard said two weeks ago. "And we've got to play him at the 4. Last time, I checked when he played the 4, he was nearly unstoppable. So I imagine he'll play at the 4 some this year, too."
While the Pacers remain hopeful Warren will be healthy enough to start the season opener on Dec. 23 against the New York Knicks, he almost certainly will miss some or all of Indiana's three preseason games. And when Warren does return, the Pacers could limit his playing time.
Last season, two-time All-Star Victor Oladipo missed the first 3½ months as he recovered from a ruptured quad tendon in his right knee. Oladipo said he's completely healthy this year.
"I would say it's night and day," Oladipo said last week. "I feel a lot better, a lot stronger. There's always room for improvement. But I feel better now, even since the bubble. I feel like I've made some pretty drastic improvements; I've just got to keep trending forward."
Sabonis also said he's ready to play, although the Pacers might play it safe with him, too.
Bowen spent most of his rookie season in the G League, playing only six games with Indiana.