NEW YORK (AFP) The US Open got underway on Monday with straight-sets wins for second seeds and tournament betting favourites Roger Federer and Kim Clijsters. But there were upsets, too, as 2001 champion Lleyton Hewitt and former world number one Dinara Safina both crashed out. Federer, seeking to regain the crown he lost to Juan Martin del Potro last year after five consecutive titles, strolled to a 6-1, 6-4, 6-2 win over Brian Dabul of Argentina in the featured night match on the Arthur Ashe Centre Court. The Swiss star, who won just his second tournament of the year in Cincinnati eight days ago, was never in trouble against the former top junior as he got back to winning ways in the tournament he totally dominated from 2004 until last years upset in the final. Ive never lost a night session match here and feel very much at home. Been in six straight finals and would like to be there again this year, but the path is long and rough, he said. I missed many break chances but credit to Brian, too. It was his first time on centre court at a major. Joining him in the second round was potential quarter-final opponent Robin Soderling, but he needed five sets to see off unheralded Austrian Andreas Haider-Maurer 7-5, 6-3, 6-7 (2/7), 5-7, 6-4 On a hot and sunny opening day there were wins also for sixth seed Nikolay Davydenko of Russia - a 6-4, 6-1, 6-3 winner over Michael Russell of the United States - and ninth seed and 2003 champion Andy Roddick, who saw off Stephane Robert of France 6-3, 6-2, 6-2 on the Americans 28th birthday. But Hewitt, at 29, found the shot-making of unpredictable Frenchman Paul-Henri Mathieu too much to cope with as he went down 6-3, 6-4, 5-7, 4-6, 6-1. It was the first time he had lost in the first round at Flushing Meadows in 11 starts and will cast further doubts on his competitiveness at the highest level of mens tennis. Clijsters, who supplied one of the sports stories of the year here 12 months ago when she stepped out of retirement and motherhood to win her second US Open title, defeated Greta Arn of Hungary 6-0, 7-5. She took the first set in just 18 minutes, but needed to fight back after going 0-4 down in the second. Clijsters said that she felt under no extra pressure to repeat her outstanding play of last year. Obviously last year I had a few more probably unanswered questions, but I think this year I know what I have to do if I want to try and do as well as I did last year, she added. There was a reasonably comfortable winning start for top American hope Venus Williams. But there were signs in her 6-4, 6-1 defeat of Italys Roberta Vinci that the 30-year-old third seed, who carries US hopes with sister Serena out injured, is still feeling some pain from the left knee injury that has sidelined her since Wimbledon. I was doing pretty good until I landed on my leg on a swing volley, she said. She didnt make a lot of errors so I was very happy to get through after not playing forever. There were wins also for fifth seed Samantha Stosur of Australia and the woman who beat her in the French Open final, sixth seed Francesca Schiavone of Italy. But former world number one Dinara Safina suffered more heartache as she attempts to return to her best form after a crippling back injury. The tall Russian put on a battling display against Slovak veteran Daniela Hantuchova, but bowed out in the end 6-3, 6-4.