Sunderland boss Steve Bruce is backing midfield duo Lee Cattermole and Lorik Cana to rediscover their best form as he battles to turn the club's season around.

The former Middlesbrough and Wigan enforcer and his Albania international sidekick laid the foundation for an excellent start to the season for the Black Cats with a series of displays which set the tone for the rest of their team-mates.

However, Cattermole suffered a knee injury during the 1-0 victory over Liverpool on October 17 and is still working his way back to full match fitness, while Cana, whose rugged approach has already cost him two suspensions, has been less influential in recent weeks.

It is no coincidence that Sunderland have struggled to maintain their encouraging opening to the campaign with two of their most influential performers out of sorts, and they will run out at Portsmouth tonight looking for a first win in 12 Barclays Premier League outings.

Asked about Cattermole, Bruce said: "It's very difficult. I know from my own experience, if you miss a big chunk of the season through injury, it takes you, in my opinion, just as long to get back.

"If you are out for six weeks, it takes you six weeks to get back to where you should be.

"In Lee's case, there is no more genuine boy than he is and he is trying his utmost - and he will get there.

"The more games he plays, the better he will become."

Cana, a £5million summer signing from Marseille, has also found the going tough after an impressive start to his career in England.

Bruce admitted: "It's caught up with him. It's the intensity because the adaptation from playing in France to here is huge.

"The intensity of the game in England is the one thing that takes some getting used to.

"But I have no problems with Lorik in terms of his commitment to the cause. I made him the captain and I have no regrets about that.

"Yes, he has suffered in the slump, if that's what you want to call it, but he will be okay, I am convinced of that."

Sunderland, who lost 2-1 at Fratton Park in the FA Cup fourth round on January 23, have slipped to within four points of the relegation zone having collected only five points from a possible 33 since they beat Arsenal at the Stadium of Light on November 21.

Bruce said: "It's quite incredible, but the Premier League can be unforgiving, I have always said it, and you can go six, eight, 10 weeks without a win very easily.

"It's happened to us. However, I have seen little signs that we can turn it around."

Sunderland will be without teenage midfielder Jordan Henderson, who will undergo a scan on his injured ankle on Thursday, but will be sidelined for at least four weeks regardless.