Walters was flattened on a hit by New York Jets free safety Jon McGraw early during the first quarter of a 31-7 rout by the Jets Saturday night in a pre-season game.
"There's a good chance he could be out for the year," said a pessimistic Colts Head Coach Tony Dungy. "We'll have to see."
"I sure would like to get him back as soon as possible," quarterback Peyton Manning said. "He was definitely playing a big role in our offense. Hopefully, he can still share in this season."
Walters, in his fourth year, was a fifth-round draft pick out of Stanford by Minnesota in the 2000 draft. Last season, he had career highs in receptions (36) and receiving yards (456).
"You feel bad for him, but someone else has to step up and someone will," Dungy said.