Healy joined the Black Cats for £1million from Fulham in the summer.
“Last Saturday was the first time in about three weeks that I have been in the squad for a game,” Healy told the Belfast Telegraph.
“There was a squad of 20 who went down to Old Trafford. As a footballer, you don’t like to be sitting at home on a Saturday watching the scores coming in on the television. You want to be playing; you want to be involved.
“I have no regrets at all about going to Sunderland. My only regret is that I haven’t played enough first-team football.
“People start questioning my ability, questioning if I am good enough. But I am big enough to take the criticism with the good and I’ve learned to live with that. I have been through a lot more lows with Northern Ireland than I have at club level.
“Given the opportunity in games and given enough time on the pitch, I still feel I am good enough to contribute and win some games to push us up the table.
“I want to perform up there; I want to prove myself to the people of Sunderland.
“I was sitting beside Niall Quinn at Old Trafford, and we’d a chat about football and the match. I want to prove to him that I am worth the money that he paid to Fulham to take me.”
