With Atletico Madrid and Real Madrid both picking up three points on Saturday, Barcelona will be under pressure to come away from Athletic Bilbao with nothing less than a victory.
Atletico pulled level with Barca courtesy their 2-0 win over Elche, with Koke and Diego Costa scoring the goals. Real Madrid were as always rampant in their La Liga match on Saturday, easing past Real Valladolid 4-0 thanks to a hat-trick from Gareth Bale, and are only three points behind the front two.
Those results have put the onus back on Barcelona to ensure they keep their three-point lead at the top of the table, and the only way they can confirm that is with a win in San Mames on Sunday.
"[Bilbao] is an aggressive side that goes for attacking football. Athletic Club are a very difficult opponent, packed with very good, very skilful players," Barcelona manager Gerardo Martino said.
Barca also have the pressure of having to bounce back from their first defeat of the season, after going down to Ajax at the Amsterdam Arena in the Champions League in midweek.
Martino is confident his side are capable of giving the right reply to the surprise loss and expects an on-fire Barca team to come out against Bilbao.
"We have to respond through football, by playing better and not repeating what we did in the first half of that game," he said. "We have to show a different face. This game will help to tell us what situation we are really in. It will demand the very best of us.
"We mustn't forget what we did against Ajax. But neither should we forget all the good things of the last three months. I'd settle for just losing one of the next twenty matches. Now we just have to show that this first defeat was not the start of anything.
"That's why Sunday's game is so important. It's a special kind of game because of what happened against Ajax. Now all we are thinking about is making sure we end the year well. And that means finishing first in our Champions League group and staying top of the league."
Barcelona have several injury worries with Lionel Messi, of course, being the biggest. The Argentine wonder is not expected to return until the New Year. In-form goalkeeper Victor Valdes is also sidelined, along with Carles Puyol, Dani Alves, Jordi Alba, Jonathan Dos Santos, Isaac Cuenca and Ibrahim Afellay.
Adriano, however, has been passed fit and is expected to feature on Sunday.
Bilbao are also in decent form this season, and will target three points as well, knowing fully well a victory will take them above Villarreal into the top four.
Key men: Athletic Bilbao: The home side will look to the playmaking skills of exciting youngster Iker Muniain, who will be keen to find the target yet again after scoring the winner against Malaga last weekend.
Barcelona: The onus will be on Neymar and Alexis Sanchez to provide the goals in the absence of Messi.
Where to Watch Live
The game is scheduled for a 1.30 am IST start on Monday early morning with live coverage on Star Sports 4 and Star Sports HD2. You can also catch the action via live streaming by clicking HERE. To watch the match live online in the U.S. click HERE. Viewers in the U.K. can click HERE. To catch the match courtesy live streaming in the Middle East and North Africa, click HERE.
Expected lineups: Athletic Bilbao: Iraizoz, Laporte, San Jose, Iraola, Balenziaga, Iturraspe, Gomez, Herrera, Rico, Muniain, Guillermo.
Barcelona: Pinto, Montoya, Pique, Mascherano, Adriano, Xavi, Busquets, Iniesta, Sanchez, Fabregas, Neymar.
Prediction: 2-1 to Barcelona