Tommy Haas continued the run of form which has taken him from outside the top 200 to world No. 36 as he beat Argentina’s Leonardo Mayer 6-4, 7-5 on Wednesday at the ATP/WTA event in Washington. The 34-year-old German fourth seed is playing some of the best tennis of his career after finally regaining full potential following a hip operation last year. He is playing for keeps this week in the US capital as he tries to bury the disappointment of missing the London Olympics. The German federation refused to nominate him for wild card tournament consideration. Haas lined up a quarter-final clash with compatriot Tobias Kamke, who earned a revenge win over Marinko Matosevic, 6-4, 6-3. The Australian had beaten Kamke last week in Los Angeles. Haas, who defeated Roger Federer to win at Halle in June, improved his 2012 record to 21-9 as he bids for a 14th career trophy. He advanced over Mayer in just over 90 minutes, hammering eight aces including two in the 11th game of the second set. The veteran, who came to Washington for the first time 15 years ago, then broke a game later to clinch the win. “It was a good win, a very hard-fought match,” said Haas. “He has a big serve and there was a lot of guessing on my part out there.