Argentine Juan Martin Del Potro ended top seed David Ferrer's reign as Japan [Images] Open champion with a 6-1, 7-5 quarter-final victory on Friday.

Andy Roddick [Images] avoided a similar fate to Ferrer, the American second seed blasting past Serbia's Viktor Troicki 6-3, 6-4 to book his place in the last four of the $969,000 Tokyo tournament.

Fifth seed Del Potro, whose heroics helped Argentina reach the Davis Cup final last month, never looked like losing his grip on the match after a hot start against world number five Ferrer.

"With Ferrer you never feel you have the edge," said Del Potro, one of several players in Tokyo chasing a berth in the season-ending Tennis Masters Cup.

"I've improved my mental preparation. I'm more positive now than before. That helped me put Ferrer away when he came back at me in the second set."

Del Potro faces fourth seed Richard Gasquet in Saturday's semi-finals after the Frenchman crushed German 12th seed Rainer Schuettler 6-3, 6-2.

LISTLESS FERRER

The 20-year-old Del Potro tore through the first set in 27 minutes against a listless Ferrer, who he is poised to play again in next month's Davis Cup final.

The lanky Argentine broke for 5-3 in the second only for Ferrer to immediately claw back the break but was unable to repel Del Potro's onslaught for long.

Sensing Ferrer's energy levels were low, Del Potro moved in for the kill as the Spaniard served at 5-6, closing out the match with a crushing forehand into the corner.

A fifth title of the year would move Del Potro into the coveted eighth spot in the year-long rankings and in line for a place at the next month's prestigious Masters Cup.

Rafael Nadal [Images], Roger Federer [Images], Novak Djokovic [Images] and Andy Murray have already qualified for the eight-man Shanghai shootout.

"I really don't care about Shanghai," said Ferrer, now in danger of losing seventh spot in the race. "It will be hard for me to get there now."

Roddick, who won his 26th ATP Tour title in Beijing [Images] at the weekend, overpowered Troicki in an hour and 20 minutes, wrapping up victory with an emphatic leaping smash.

"That's the best I've hit the ball this week," said the former U.S. Open champion. "I didn't serve as well as the last two days but I played better from the baseline.

"Hopefully I can put the two together on the weekend."

The American next meets the winner of Friday's last quarter-finals between third seed Fernando Gonzalez of Chile and Czech ninth seed Tomas Berdych.

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