Tokyo, Japan -- (Sports Network) - Argentine Juan Martin Del Potro upset top- seeded Spaniard David Ferrer to reach the semifinals at the $869,000 Japan Open Tennis Championships.

The fifth-seeded Del Potro earned a 6-1, 7-5 win to beat last year's champion. Del Potro, who turned 20 years of age on September 23, is making a quick rise in the top 10 of the world. By winning the Tokyo title he can overtake James Blake at No. 8. The victory Friday was Del Potro's 28th in his last 29 matches.

"The first set looked easy, but I knew it was going to be harder than that because [Ferrer] is a warrior and fights until the last point," said del Potro.

Ferrer had won their two previous meetings, both this year, at the Australian Open, where del Potro retired trailing by two sets, and at 's-Hertogenbosch in the semifinals.

"I am not surprised by how he played," remarked Ferrer. "He has so much confidence right now winning all these matches the last two months. Today he served very well on important points. That was the difference."

American Andy Roddick, the second seed, was a 6-3, 6-4 winner over Serbian Viktor Troicki. Roddick is trying for his fourth title of the year and second in a row, having captured the Beijing crown last week.

"I did not feel very comfortable during my first match here, but now I know I can get through the weekend if I keep playing like this," said Roddick, who had a first-round bye and played three tiebreakers to beat Ivo Minar in the second round.

The next opponent for Roddick will be ninth-seeded Czech Tomas Berdych, who thumped third-seeded Chilean Fernando Gonzalez, 6-0, 6-4, in a mere 62 minutes.

Del Potro's semifinal foe will be fourth seed Richard Gasquet of France. Gasquet defeated 12th seed Rainer Schuettler of Germany, 6-3, 6-2. Schuettler titled here back in 2003.

The 2008 Tokyo champion will collect $135,000.