Barcelona assistant manager Jordi Roura says his side will have to balance attacking intent with caution if they are to progress to the Champions League quarter-finals against AC Milan tomorrow night. The Catalans were again not in sparkling form as they beat bottom-placed Deportivo La Coruna 2-0 to extend their lead at the top of the Spanish standings to 14 points. Lionel Messi came off the bench to score for a world record-beating 17th consecutive league game. However, with a 2-0 deficit from the first leg in Italy to overcome, Roura is wary of conceding an away goal. "There is no doubt on Tuesday we have to attack because we have to score goals," he said. "But we also can't get over-excited. We have to balance our need to go forward with being careful at the back. "We know how Milan are going to play and how we are going to play. All the players are very concentrated and we know how important a game this is." With Milan in mind, Barca made seven changes to the side who had started the 2-1 defeat to Real Madrid the previous weekend with Messi, Andres Iniesta and Gerard Pique among those who started on the bench. However, they were still dominant in the first half and after a number of fine saves from Daniel Aranzubia had frustrated the hosts, Alexis Sanchez headed them into a deserved lead seven minutes before the break. After half-time though, Barca were far from fluent and Roura had to introduce Messi and Iniesta in a bid to kill the game off, which Messi duly did with two minutes remaining with a lovely dinked finish to register his 40th league goal of the season. The biggest bonus for Barca ahead of tomorrow was the fact that they kept a clean sheet for the first time in 14 games and while acknowledging they face a much stiffer test against Milan, Roura was delighted to finally end their streak of conceding goals. "Every competition is different, but the best way to prepare for that game has been to play well and certainly to not concede," he said. One of those who did not shine, though, was Cesc Fabregas as he was booed by sections of the home support when being replaced by Sergio Busquets in the second half after another disappointing performance. "The fans are allowed to say what they want and every player will have his good and bad moments in the season, but we are delighted with Cesc and he is a player with undoubted quality," Roura said. Deportivo manager Fernando Vazquez, meanwhile, lamented his side's inability to create anything of note given Barca's defensive problems of late. "We didn't create enough opportunities. Barcelona defended well, pressured well and we couldn't get out," he said.