Indianapolis Colts quarterback Andrew Luck is "legitimately questionable" to play Sunday against the Jacksonville Jaguars, according to ESPN's Adam Schefter.

The 26-year-old has been hampered all week with a right shoulder injury.

Schefter says the Colts pivot threw before practice, but didn't participate in any team drills and is unlikely to throw again before Sunday. 

If Luck can't go, 40-year-old Matt Hasselbeck would get the nod for the 1-2 Colts. 

Luck has not missed a game in his four-year career. The former first overall pick has struggled so far this year, throwing for 753 yards, five touchdowns, and seven interceptions through three games.

In a move likely made in case Luck does miss Sunday's game, the Colts signed quarterback Josh Johnson to their 53-man roster on Friday. If Luck is inactive, Johnson will serve as Hasselbeck's backup.

After Jacksonville, Indy has a short week with a clash against the Houston Texans on Thursday.