Romanian international Pantilimon left the Etihad Stadium over the summer, having made just seven appearances for City after joining the club in 2011.
Signing for the reigning Premier League champions originally on loan, he failed to make a single league appearance in his first or second year in Manchester, finally making his debut in November 2013, deputising for an out-of-form Joe Hart in a tie with Norwich City.
Whilst he was signed as a back-up keeper, the 27-year-old was seemingly keen on securing his playing future as last season drew to a close, and, with a number of clubs keen on his signature, it was considered quite a coup for Sunderland to sign the stopper on a free transfer.
He arrived at the Stadium of Light in a period of upheaval, as head coach Gus Poyet looked to make his mark on the team after securing their Premier League status with a squad compiled by ex-coach Paolo Di Canio. First-choice goalkeeper Vito Mannone - signed by Di Canio - had performed admirably for the Black Cats in their remarkable fight for top flight survivial, and it was the Italian who kept his starting role for the opening fixture of this season - relegation Pantilimon to the bench once again.
However, a series of high-profile mistakes - including a despairing display in the 8-0 defeat at Southampton - saw Poyet drop Mannone for the victory over Crystal Palace, and Pantilimon kept his place between the sticks for the draw with Everton prior to the international break. It is likely that the Romanian will continue in the starting XI when the Premier League returns this weekend, and Poyet admitted that he has been outstanding in training, having been told that he was not guaranteed football when he signed for the Black Cats.
Speaking to the Chronicle, Poyet said: “I brought Costel in and I have to say that I told him before he came that I couldn’t promise him to play.
“He was leaving Man City and he was looking for a place to go and play. I said ‘if you want it easy, this is not the place’.
“But he knew, he came, he did well in pre-season and thought he had a chance.
“I think of course he wanted to play which was good. Then he was upset, which was good.
“But then he got on with it professionally and to be honest, in training, he was outstanding which is good.”