Saturday's home win over Arsenal saw McCartney (pictured) produce probably his best performance since returning to the Black Cats last season.

He has struggled with a succession of foot and hamstring injuries, which have severely limited his availability.

Boss Steve Bruce is likely to rekindle his interest in Wigan left-back Maynor Figueroa in the January transfer window, so McCartney could be entering a vital few weeks in his Sunderland career and pulled no punches about his situation.

The honest Northern Ireland international said: "I wouldn't say I've been 100 per cent fit yet.

"I had a hamstring injury a few weeks back and I was still having problems at the start of the season.

"Since I have come back to Sunderland, it has been a nightmare. It's been a matter of me trying to keep myself fit and train every day, which I haven't been able to do to this point.

"I want to stay in the team and play as many matches as I can because I know what I'm capable of doing.

"But, with the injuries, I haven't shown that yet.

"I'm sure in time, when I get myself fit again, I'll be able to show what I can do. I'm not really happy with how things have gone, but I'm happy to be at Sunderland."

The weekend's triumph over Arsenal means that Sunderland have played all of last season's top four and lost to only one of them – Chelsea.

Yet they have come unstuck with losses at Burnley, Birmingham and Stoke.

Despite that, McCartney predicts his side will be in a confident mood heading this Saturday to Wigan – who were embarrassed 9-1 at Spurs on Sunday.

"This year we've beaten the top teams and we're going into the Wigan game thinking it's one of the easier matches – no disrespect to Wigan," he said.

"It's certainly a game we feel we should be winning.

"They had an amazing result at the weekend. We played Tottenham recently and I wasn't too impressed with them, but to beat any Premier League team by nine takes some doing.

"Obviously, Wigan will be hurting and will be looking to put it right this week.

"It will be a very difficult game, especially at their place and their manager will have them right up for it.

"We have been performing really well over the last few weeks without getting the results – that changed on Saturday (against Arsenal).

"Hopefully we can go into the Wigan game with that extra bit of confidence because of it."