The 24-year-old has a stress fracture in his lower leg and may miss as many as three or four games, including the Ranfurly Shield match against Canterbury on August 27.
He picked up the injury while in Japan with the Blues playing in a warm-up game before the ill-fated match against the Sunwolves which the Blues lost 48-21.
News of Collins' injury comes a day after hooker and co-captain Liam Coltman was ruled out for the season with an ankle complaint.
Otago coach Cory Brown said Collins would miss ''the first section of the Mitre 10 Cup'' and ''we will see how he is going and how it is looking when we re-scan it in about six weeks''.
Brown said there was plenty of cover in the squad with outside backs Leroy van Dam and Josh Timu joining the squad recently.
Vilimoni Koroi, Jona Nareki, Matt Faddes and Josh Ioane could all slot into fullback as well.
''So we have a few options there but it is just about making sure we have the balance throughout the rest of the squad,'' Brown said.
With Coltman ruled out, Sam Anderson-Heather will captain the side on his own with possibly Tei Walden deputising.
With lock Tom Franklin and loose forward Paul Grant playing elsewhere, and Coltman injured, Otago has shed 181 caps this season.
Otago plays North Harbour in Albany on August 17.