LOS ANGELES (Reuters) - Sam Querrey reached his third consecutive ATP final by upsetting top-seeded German Tommy Haas 6-3 7-5 at the LA Open on Saturday. The big-serving American, seeded sixth in the hardcourt event at the LA Tennis Center, broke the twice champion once in each set to seal victory in one hour, 30 minutes and will be hoping to improve on his two runner-up finishes in July. Querrey will meet qualifier Carsten Ball in Sunday's final, the little-known Australian continuing his fairytale run in Los Angeles with a 7-5 7-6 win against Argentina's Leonardo Mayer. Haas, champion here in 2004 and 2006, was broken in the eighth game of his semi-final when the German hit a backhand long off a Querrey net cord and the American coolly served out in the ninth to take the opening set. The second set went with serve with a key moment coming in the eighth game, when world number 22 Haas squandered two break points and promptly hurled his racket to the ground in disgust. Although 32nd-ranked Querrey failed to capitalise on three break points in the ninth, he broke in the 11th when Haas dumped a forehand volley into the net after being in control of the rally. Serving for the match at 6-5, Querrey trailed 0-40 before coming back to clinch victory when Haas struck a backhand into the net. "I have played a lot of matches, 15 or 16 in the last three or four weeks, and that helps," Querry told reporters after beating Haas for only the second time in five career meetings. "The more matches you win, the more confident you are and things are just rolling one for me at the moment." KEPT COMPOSURE Asked how he had kept his composure after slipping behind when serving for the match, the 21-year-old replied: "I just slowed it down. "I took it one point at a time and my buddies back here helped me through," Querrey added, referring to his loyal group of self-billed 'Sam-urai" supporters. "I knew I had to serve well and I was trying to be aggressive on his service games. He's got a big second serve with a lot of slice and I just told myself to take chances." Left-hander Ball, the world number 205 who had never won a match on the circuit until this week, reached his first ATP final by clinching the second-set tiebreak 7-3 when a Mayer forehand sailed wide. Having come through three matches of qualifying to book his place in the main draw, the 22-year-old punched his left fist into the air to celebrate his achievement in front of his proud parents and a cheering crowd. "It's definitely been a surprise and something we all work for and finally a good week has come," Ball said with a grin, having broken Mayer in the 12th game to clinch the first set. "These are good conditions here for my game. The court bounces high, I get a lot of kick and spin off the court and yet it's fast enough to play aggressively and get in to the net."