Arsenal striker Robin van Persie says victory over Fulham this weekend is crucial if they want to challenge for the title."It is very, very tough," he said. "I saw the game against Everton and they were very decent and it was a very good goal from Damien Duff. It's going to be hard but as long as we can put the pressure on the opponent, play together and share the goals then I'm quite confident."If you look last year, the way Manchester United became champions was against the smaller teams."They won against all the teams from 19 to 10. That is why they became champions. So it is very important to win these games maybe even more in the end."