But despite the two-to-six-week timeline, the Colts are prepared for Luck to be sidelined longer than the minimum projection, sources told Werder.
The San Diego Chargers placed star wide receiver Keenan Allen on season-ending injured reserve last week with a lacerated kidney because they were told he wouldn't recover for at least six weeks and would not be cleared for contact even then.
Luck and Allen play different positions, and it is not clear whether the severity of their injuries is the same, league sources told Werder.
Colts coach Chuck Pagano said Tuesday that Luck likely will not need surgery but called the injury "one heck of a blow."
"You don't want to lose anybody, especially your starting quarterback," Pagano said. "Our guys will respond like they always do. We've been through a ton already this season and in the past, and we'll get through it."
Luck, according to Pagano, was injured when he scrambled on a second-and-9 play and took a hit from Denver linebacker Danny Trevathan in the fourth quarter Sunday. Luck remained in the game and threw a touchdown pass to Ahmad Bradshaw on the next play.
Veteran Matt Hasselbeck will start at quarterback during Luck's absence. Hasselbeck, 40, won both of his starts earlier this season when Luck was out with a right shoulder injury.
The Colts, who lead the AFC South with a 4-5 record, have a bye this weekend and play at Atlanta on Nov. 22.
ESPN.com Colts reporter Mike Wells contributed to this report.