Pakistan defeated Kenya comfortably in their first match of the World Cup but skipper Shahid Afridi said his side will have to play with lot more energy if they desire to beat mighty Sri Lanka in front of their home crowd on Saturday. Pakistan opened their World Cup campaign with a thumping 205-run win over unimpressive Kenya in group A here last night but Afridi said they cannot afford to relax at any point in the tournament. "It's a good start but we shouldn't be 100 per cent satisfied. There is a lot of work ahead of us still. Good teams are coming up but there are positive points from this match for the next games," he said at the post-match press conference.