Updated

NEW YORK (Reuters) - Peyton Manning's National Football League season was put in doubt as the Indianapolis Colts said the quarterback would miss an unspecified amount of time after undergoing his third neck surgery in 19 months.

The four-time most valuable player, who was already ruled out of his team's season opener this Sunday having not fully recovered from a previous neck operation in May, will begin a rehabilitation regimen immediately, according to the Colts.

"This procedure is performed regularly throughout the country on persons from all walks of life, including professional football players," the Colts, who called the surgery "uneventful," said in a statement.

"Two former Colts players had this same procedure last winter and have fully resumed their careers. Rehabilitation from such surgery is typically an involved process. Therefore, there will be no estimation of a return date at this time."

Manning will remain on the Colts' active roster until the team has a clearer picture of his recovery process.

Earlier on Thursday, Colts owner Jim Irsay tweeted that Manning was likely to be out awhile.

Irsay posted: "We had a good practice yesterday and r guys r fired up 4 the season. (hash)18's out for awhile, but compete, we will/BELIEVE."

LENGTHY ABSENCE

Dr. Victor Khabie, a sports medicine specialist at Northern Westchester Hospital, said he expected Manning to miss at least eight weeks, if not the entire season.

"Having two cervical spine procedures so close together definitely sets him back significantly and entails a prolonged healing process," Khabie told Reuters.

"Recovering to the level required to perform as an NFL quarterback can take significant time. Nerves tend to recover slowly and this could mean he could be out for a while before his throwing arm to returns to full strength."

Manning was on the sidelines for most of the pre-season after undergoing neck surgery in May and was only recently taken off the physically unable to perform list, which allowed for some limited practice.

However, on Monday the team listed him as doubtful for Sunday's game, saying the recovery from his neck operation had slowed and that he must stop practice. The Colts then said on Wednesday that Manning was ruled out of the season opener.

"To say I am disappointed in not being able to play is an understatement," Manning said in a statement. "I simply am not healthy enough to play, and I am doing everything I can to get my health back."

Manning's absence on Sunday ends a run of 227 consecutive NFL games, including playoffs, which is the second longest streak for an NFL a quarterback, behind the now-retired Brett Favre (297).

In his place, 16-year veteran Kerry Collins will be the starting quarterback. Collins retired from the NFL in July but the Colts agreed to terms with him last month given the uncertainty surrounding Manning's health.

(Writing by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)