The center back has returned to Argentina to be assessed by the national side's medical team after he broke two bones in his back during an acrobatic clearance.
The center back suffered the injury while acrobatically clearing the ball during Newcastle's 4-2 win over Southampton at St James' Park on Feb. 24 and has not featured for the club since.
Newcastle manager Alan Pardew has confirmed the 31-year-old Coloccini has returned to Argentina to be assessed by the national side’s medical team, and he could be out until May.
"Colo has gone back to Argentina,” Pardew told reporters. “There's no treatment he can have, he's broken two of the bones in his back.
"We think it's going to be anything between three and seven weeks. He's gone back for a week."