Coach Tito Vilanova wants Barcelona to focus on Tuesday's match against Benfica and not be distracted by Madrid's visit to the Camp Nou on Sunday.
Barcelona matched its best Spanish league start with a comeback 3-2 win at Sevilla on Saturday, and coach Tito Vilanova wants his team to focus on the Portuguese club and not be distracted by Madrid's visit to the Camp Nou on Sunday.
"The game in the Champions League will be more complicated than the game against Madrid," Vilanova said. "This game is not a moment to hold something back.
"We have to go to Lisbon looking to win. Benfica is an important team. (Last season) they deserved to move past Chelsea, which then went on to win the tournament."
Also, Spartak Moscow hosts Celtic looking for its first victory in the other Group G match.
Four-time champion Barcelona leads the group with three points. Celtic and Benfica are second with one point each.
Lionel Messi has scored 10 goals in nine games for Barcelona this season. His team needed Messi's late goals to beat Spartak at home in its first match. Since then, the Argentina forward has gone two outings without finding the back of the net.
Last weekend, Sevilla's defence was successful at stopping Messi from scoring, so he turned playmaker to assist Cesc Fabregas and David Villa for two goals in the last four minutes to secure Barcelona's sixth win in as many league games.
"It is increasingly difficult. We want to attack but teams play farther and farther back in their area," Messi told Spanish newspaper El Pais.
"Our opponents know us well and look for our weak points, and if they are lucky and score off a counter-attack, they can make things difficult for us."
Barcelona will be bolstered by the return of Andres Iniesta, Carles Puyol and Adriano from injury, while midfielder Thiago Alcantara will be sidelined for two months after hurting a ligament in his right knee in Seville.
Benfica may be the leader of the Portuguese league, but it is winless in its last 12 games against Spanish competition.
"We know we're going to have to run a lot," Benfica coach Jorge Jesus said after his team's 2-1 win over Pacos Ferreira on Friday. "Barcelona will wear us down. It's going to be a very intense game."
Benfica will be without first-choice centre forward Oscar Cardozo because of injury, while its midfield has been weakened by the recent transfers of Javi Garcia to Manchester City and Axel Witsel to Zenit St Petersburg.
With Barcelona favoured to win at Benfica, Spartak has a good opportunity to move into position to fight for second against Celtic.
Spartak Moscow rallied to beat Amkar in the Russian League 3-1 Saturday and is tied for fourth place in the standings.