FOX Sports' Jay Glazer first reported the news.
Luck had what the Colts believed was a mild setback more than two weeks ago, when he experienced soreness in his throwing shoulder after he was cleared to practice. He received a cortisone injection for the pain at that time and proceeded to have a good week of rehab, only to experience another setback, which the team does not believe is serious, a source said.
Nevertheless, Luck's recovery from surgery to repair a torn labrum on Jan. 15 is clearly an unforeseen development and the quarterback finally decided to seek additional opinions. One of those visits to a specialist is scheduled for Monday, the source added.
The additional exams likely will determine whether he should resume his rehab in an effort to play this season, according to the source, but the prospect of Luck playing this season has unquestionably grown dimmer.