Colts observations: Anthony Castonzo injury a setback for Colts' offensive line

Insiders Stephen Holder and Zak Keefer discuss Andrew Luck's progress and what Anthony Castonzo's injury means to the offensive line. Clark Wade/IndyStar

WESTFIELD – Just as the Colts’ offensive line was starting to take shape, they now face their first setback of the season.

Veteran left tackle Anthony Castonzo, who left Friday’s practice with a sore hamstring, will be sidelined for an undetermined period of time, according to coach Frank Reich. While Reich did not specify an exact length of time on Castonzo’s absence – which appears to be the result of a recurrence of the same issue that caused him to miss the start of camp – Reich suggested it might not be brief.

“He’s going to miss a…