Sunderland boss David Moyes has ruled out goalkeeper Vito Mannone for three months with an elbow injury.
The 28-year-old was sent for a scan after hurting his arm during training and was found to have sustained ligament damage.
"Vito has torn ligaments in his elbow and we're waiting to see whether it will require surgery," Moyes said on Friday, before adding that the former Arsenal man would miss "a minimum of three months".
Moyes confirmed he would be looking to sign another goalkeeper before next week's transfer deadline in order to provide back-up to England youth international Jordan Pickford.
"We definitely need to look for another goalkeeper because we only have a young keeper after Jordan Pickford," he said.
"Jordan now has his chance to show what he can do. He has a big future ahead of him."
Moyes also confirmed that a bid has been lodged for Sevilla midfielder Vicente Iborra, after reports this week claimed that a £7million offer had been accepted by the Europa League holders.
New signing Javi Manquillo, meanwhile, is in line for his Premier League debut for the club against Southampton on Saturday, while Lamine Kone faces a late fitness test on a back problem.
Jan Kirchhoff and John O'Shea are set to miss out, however, as Sunderland chase their first points of the season at St Mary's Stadium.
"If we can go to Southampton and get a point it would be a good result, but we want to go there and win," said Moyes. "I thought Southampton played really well at [Manchester] United and thought they were unlucky. The club have a real solidity about them.
"There's a good chance Manquillo could start this weekend. We will train this afternoon and have a look at Lamine Kone then.
"I hope Kirchhoff will be back after the international break. O'Shea has a hip problem, we hope Fabio [Borini] will be back this weekend."