Stan Wawrinka shakes off form slump to thrash Tomas Berdych at ATP World Tour Finals "I didn't expect to win that easy in the score, for sure": Stanislas Wawrinka celebrates after the win. Form slump? What form slump? Despite having won a single match in his previous four tournaments, Australian Open champion Stan Wawrinka dominated his first at the ATP World Tour Finals, thrashing Tomas Berdych 6-1, 6-1 in just 58 minutes. It was the third match from three at the season finale that failed to go the three-set distance, but a welcome reversal of fortunes for the Swiss third seed, whose only non-Davis Cup victory since reaching the US Open quarter-finals had been over young Austrian Dominic Thiem at the recent Paris Masters. "I didn't expect to win that easy in the score, for sure," said Wawrinka, who reached the semi-finals on debut here last year, and this season has won three titles, including his maiden grand slam at Melbourne Park, but none since the Monte-Carlo Masters in April. "It was my worst match of the whole season": Tomas Berdych. But I was ready to play well. I did a great week of preparation. Even if the result wasn't there in Basel and Paris, I was feeling the ball really well at the practice court. And, on Monday, on the 02 match court. Berdych has now dropped his opening round-robin match at all five of his World Tour Finals appearances, and this one was a shocker. The Czech world No.7 won just five of 21 points on his second serve, and did not manage a single groundstroke winner among 20 unforced errors. Well, unfortunately it was my worst match of the whole season, and I kept it for the start here in the World Tour Finals. So that's not the best one at the start," Berdych said. But, yeah, there are days like that. Now it's over. Really, I mean, it's just matter of looking forward, trying to find a way for next few days. Just try to leave this somewhere very far and try to come up with some better tennis. Wawrinka led 4-0 after just 15 minutes, losing just one point all match on his first serve, and landing an early blow in the battle for what is tipped to be the second semi-final place behind Group A favourite Novak Djokovic, who was due to headline the evening session against Marin Cilic. Wawrinka's Swiss teammate at next week's Davis Cup final in France, Roger Federer, and US Open runner-up Kei Nishikori were the Group B winners on Sunday, against Milos Raonic and Andy Murray respectively.