The Irish striker had returned from a loan with Southend United and remains available at Sunderland.
He told the club's official website, safc.com: "It's the first time in a long time I have felt sharp and almost back to myself.
"I think I'm just about getting a run together now. I had appendicitis at Blackpool last year and that knocked me back.
"I haven't played that much football in the last year and a bit.
"It's nice to get a run of games together. Hopefully I carry on getting a run of games now and get my career going again."