Barcelona defender Carles Puyol has called on his team's fans to do their bit in the second leg of their tough UEFA Champions League quarter-final against AC Milan. The first leg ended in a goalless draw at the San Siro last night as two of Europe's heavyweights slugged it out for a place in the semi-finals. Puyol helped his side keep a clean sheet in Italy and believes Barça's fans can help them win the second leg at the Camp Nou. Puyol said of the return leg on the club's website: "It will be one of the best games. They are aware of what is at stake and I'm sure they'll be with us from the first minute." Barcelona dominated possession in last night's game but the best chance fell early on to Milan's Robinho, who volleyed high and wide when the ball fell to him in the penalty area. The visitors were denied what they thought was a penalty when Christian Abbiati brought down Alexis Sanchez, but referee Jonas Eriksson ignored their claims. Puyol also thought he had been fouled in the area as he lined up a diving header from a corner which went across goal and narrowly wide. The defender explained: "I broke free but I noticed that someone was grabbing my shirt. I pointed it out to the referee and he told me that it wasn't a penalty. However, we cannot look for excuses. We have to play well, refereeing is very difficult." Goalkeeper Victor Valdes admitted if Barcelona had scored an away goal it would have made their job a lot easier in the second leg. He said: "We had many chances to score. We had a lot of possession but we weren't able to capitalise on the chances we created. It's a shame. It's always important to score away from home but now it's time to work hard and, especially, defend well." Valdes also backed the approach of coach Pep Guardiola if Barcelona have to adopt defensive tactics. "Like the boss says, if we have to play with nine defenders we will, but we have to win," he added. Mascherano, Messi bemoan pitch Barça forward Lionel Messi believes his side face a difficult test going into the second leg. "It's a dangerous situation. Either team could go through, we hope we can score so it will be us. We deserved to win," said the three-time FIFA Ballon d'Or winner. Several of the Barça players found the San Siro pitch to be slippery and struggled as a result. "We played our game but it was difficult because of the pitch and because they are very strong," said the Argentinian. Team-mate Javier Mascherano also found it difficult to play on the San Siro surface. He said: "The pitch was a problem in the stadium and it affects other teams. "It's the result that we finished with, I believe that we deserved more. If we play next week's match like today, I'm sure we'll go through."