SUNDERLAND take on Bournemouth in a relegation battle that could define their season this afternoon, with Sam Allardyce admitting a defeat would leave his side facing a huge challenge to avoid the drop.

A month or so ago, the Black Cats looked to have turned the corner when they clambered out of the bottom three for the first time on Allardyce’s watch, but a run of five successive victories quickly plunged them back into deep trouble.

Back-to-back victories over Aston Villa and Swansea steadied the ship, but with the majority of their relegation rivals beginning to find some form, last weekend’s defeat at Tottenham plunged Sunderland back into 19th position, four points adrift of safety.

Today’s opponents, who were touted as one of the favourites for relegation at the start of the campaign, are six points above them, and while there is still almost four months of the season to go, Allardyce admits the gap would become all-but-unbridgeable if Sunderland were to suffer a sixth Premier League home defeat this afternoon.

“We need to have the same attitude that we showed against Aston Villa and Swansea, and we need Jermain Defoe to have his shooting boots on again,” said the Black Cats boss. “If those things happen, then hopefully we’ll be fine and we’ll be able to secure what would be three very precious points.

“At all costs, we cannot afford to lose this game. We have to try to win it, but we certainly can’t afford to lose. If that happened, the distance between us and Bournemouth would be massive.

“We’d be nine points behind them, and when you are at the bottom and have only won five games all season, then to say you’d have to win three games just to catch them up would be a huge task. For that reason, there’s far more pressure on us.”

Sunderland handled that pressure against Villa and Swansea, successfully coping with being pegged back in both games to come away with six priceless points.

They will have to display similar resolve today, with Bournemouth having lost just two of their last 11 matches in all competitions.

Allardyce was disappointed with his side’s second-half capitulation at Tottenham last weekend, but concedes it was always going to be a tough task to take anything from Spurs. For all that Bournemouth have been playing well in recent weeks, today’s game is a completely different story.

“When you’re playing in these games, it’s all about managing the mentality side of things,” he said. “It’s about being focused mentally to produce your best performance.

“Hopefully, we’ll continue how we left off against Villa and Swansea because it’s the six-pointer that invariably comes up at this time of the season yet again. If we can continue to win those, it will help us get out of the problem we’re in.”

Two members of Sunderland’s likely starting line-up have experience of life at Bournemouth, as both Defoe and John O’Shea spent time on loan at the south coast club at the start of their career.

Back then, the Cherries were almost going out of business in the lower reaches of the Football League, but they have undergone a remarkable transformation in the last few years that has seen them climb into the top-flight for the first time in their history.

They have spent more than £18m to recruit Benik Afobe and Lewis Grabban this month – a sum that would have been unthinkable even a couple of seasons ago – and Allardyce feels their manager, Eddie Howe, deserves a large amount of credit for his role in the club’s dramatic progression.

“I think Eddie’s also been progressing steadily over a few years now,” he said. “Even though he still looks very young and handsome - not as haggard as most of us when we do this job!

“His experiences over the years have shown he’s very confident as a manager, and now he’s at the top level of his industry. It’s great credit to him and the club as a whole on what they’ve achieved.

“I’m sure as they go along, his main priority is to try and maintain their Premier League status. They’ve spent a few bob now and the team has overcome a difficult start, and he, his coaching staff and his team seem to have got used to what needs to be done to get a result in the Premier League.”

Dame N’Doye is likely to make his Sunderland debut at some stage this afternoon, but the striker, who has signed a season-long loan from Trabzonspor, is likely to start on the bench.

With Vito Mannone returning to the starting line-up in place of Jordan Pickford, and Younes Kaboul and Seb Larsson still unavailable because of injury, Allardyce is expected to revert to the side that did so well in the 4-2 win at the Liberty Stadium earlier this month.