Manning did some light therapy and watched a portion of Friday's practice but there were no plans for him to attend Sunday's home opener against the Cleveland Browns.
Doctors have told him he needs to rest his body and mind and there's no safe haven with a large crowd and certainly not in the bench area at Lucas Oil Stadium.
FoxSports' Jay Glazer reported during Sunday's pregame show that Manning flew to Europe to undergo stem-cell therapy prior to his most recent surgery. The treatment is not yet used in the United States.
Manning will begin a next-level rehab and a limited level of football activity, presumably watching plenty of practice and game tape.
Without Manning and linebacker Gary Brackett on Sunday, the Colts lost 27-19 and fell to 0-2.
Cleveland was without tackle Tony Pashos, who is dealing with an ankle injury. He's joined on the inactive list by quarterback Thaddeus Lewis, receiver Carlton Mitchell, defensive back Eric Hagg, linebacker Titus Brown, offensive lineman Steve Vallos and tight end Jordan Cameron.
Chris Mortensen is ESPN's senior NFL analyst. Information from The Associated Press contributed to this report.