SUNDERLAND boss Regis Le Bris admits the return to fitness of centre-half Dan Ballard has given him a "problem" moving forward.

After missing the first couple of weeks of the season following summer knee surgery, Ballard was back on the bench for Saturday's game against Burnley and came on for the dying minutes to help the Black Cats see out their deserved 1-0 success.

It was a third successive clean sheet for table-topping Sunderland, with Le Bris having unsurprisingly stuck with the same back four for every league game so far.

Trai Hume and Dennis Cirkin have impressed at full-back, while Aji Alese has taken his chance alongside Luke O'Nien in the heart of the defence in the absence of Ballard.

But with the former Arsenal man now fit and available, Le Bris has some tricky selection calls in the coming weeks.

Ballard has been immense for Sunderland since moving to Wearside two years ago and committed his long-term future to the Black Cats in the summer amid interest from Premier League clubs.

But it would still be a big call for Le Bris to drop either Alese or club captain O'Nien on the back of three successive shut-outs.

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The wise money would be on Alese and O'Nien again starting at centre-back at Portsmouth this weekend.

But it will be interesting to see what Le Bris does when Sunderland head for Plymouth after the international break, by which time Ballard will have a good few weeks of training under his belt.

"It is a good problem for me because if we have good competition across the team, they will push themselves and each other," said the head coach.

"When one is missing, the whole level of the team can be high. The players who aren’t selected, they will work well and they will be involved next game. The season is very long and those who haven't been in the squad will have an opportunity."

Sunderland's defensive solidity has been one of the big plus points for Le Bris in the first few weeks of the season. Burnley headed for the Stadium of Light on Saturday having scored nine goals in their first two games but Scott Parker's Clarets only managed four shots on Sunderland's goal, with Anthony Patterson having just one save to make.

The trip to Portsmouth is another tough test for the Black Cats. While Pompey are still looking for their first win of the season, they've drawn against Leeds, Luton and Middlesbrough, who were all fancied to be in the promotion mix before a ball was kicked this season.

Le Bris said: "I am very happy with the clean sheets. The organisation of our team is the key to succeed.

"The difference part of our game is getting better. It wasn’t perfect against Burnley. At the end of the first half we had to be higher, but the crowd were with us and they felt the energy and cohesion inside the team."

While delighted with his side's start, Le Bris is stressing to his players that they haven't achieved anything yet and must strive to keep improving.

“It’s good for the dynamic but it is after three rounds," he said.

"It’s better to have nine points than one, two or three, it is good for confidence in the way we work, but let’s sustain the level and keep improving.

“We want to improve details and that can change the face of the game.

”The connections here are good. The important thing is we are working together, we are in the same direction. Sometimes we will win and sometimes we will lose, but we want to improve, that’s most important."