Reich told reporters that Wentz's latest ailment resulted from an old injury -- possibly from high school -- and a broken bone came loose in the signal-caller's left foot.
Colts offensive coordinator Marcus Brady said Friday that Wentz felt a "twinge in his foot" when he rolled out and planted to make a throw late in Thursday's training camp practice. He was held out for the final period of that practice due to the injury.
The Colts then met with multiple doctors to determine the best course of action, with all parties involved agreeing that surgery was necessary to ensure the injury didn't return. The procedure will remove the bone out of the fifth metatarsal of Wentz's left foot.
"I think it was a gut punch for him for about two hours," Reich said.
Reich said the wide range of the recovery timetable is because players have different recovery rates. The franchise could have a better understanding on Wentz's return once he begins the rehabilitation process.
"Knowing Carson, I'm optimistic," Reich said. "Knowing this is the type of injury you don't have to be pain-free to play in. You have to get to an acceptable level of tolerating pain and then you can start playing. That could happen early."
The Colts acquired Wentz from the Philadelphia Eagles during the off-season, reuniting him with Reich. The Eagles received a third-round pick in this year's NFL Draft and a conditional second-round choice in the 2022 draft for the 2017 Pro Bowl quarterback.
The 28-year-old Wentz was benched in favor of Eagles rookie Jalen Hurts last season after being sacked 50 times and tossing 15 interceptions over just 12 games.
Wentz, who sustained a season-ending torn ACL late in the 2017 campaign, has played a full NFL season only twice in his career.
Jacob Eason, Sam Ehlinger, Jalen Morton and Brett Hundley, who was signed Saturday, are the other quarterbacks on the Colts' roster.