Jo-Wilfried Tsonga boosted his chances of qualifying for the ATP World Tour finals by reaching the Japan Open semi-final.

The big-hitting Frenchman, who is currently ranked seventh in the rankings with eight to qualify for the season-ending event, battled from a set down to defeat Ernests Gulbis at the Rakuten Japan Open in Tokyo.

Latvian Gulbis was tipped for big things when he climbed into the top 100 as an 18-year-old but his progress since has been disappointing.

There is no doubting his talent, though, and, after coming through qualifying in the Japanese capital, he had impressed on his run to the last eight.

Second seed Tsonga would have known to expect a battle after struggling against Gulbis, now 21, in Bangkok last week.

And it was the same story today as the Latvian began well before eventually going down 4-6 6-4 6-3.

Tsonga will meet fourth seed Gael Monfils in the semi-finals after he, too, came through a tough match against Stanislas Wawrinka.

The Swiss raced through the first set but Frenchman Monfils recovered well to triumph 2-6 6-3 6-4.

Defending champion Tomas Berdych saw his hopes of a second successive Tokyo title dashed by Mikhail Youzhny, the Russian winning 6-2 7-6 (8/6).

The final last-eight clash resulted in an easy win for 2001 champion Lleyton Hewitt over qualifier Edouard Roger-Vasselin.

The Frenchman had dumped out US Open champion and top seed Juan Martin Del Potro in round one but was no match for Hewitt, who cruised through 6-4 6-0.