The exit of number three Wawrinka in 71 minutes followed the loss of fourth seed Juan Ignacio Chela, who was beaten by Bulgarian youngster Grigor Dimitrov 6-2, 5-7, 6-1.

With the Wednesday defeat of second seed Juan Martin Del Potro in an opening match against American James Blake, French top seed Gael Monfils remains the last of the elite still in contention at the Kungligahallen.

Wawrinka, ranked 19th, suffered another year of bad luck in the capital after losing a year ago in the quarterfinals to Swiss compatriot Roger Federer.

Wawrinka smashed a racquet near the end of his ordeal against Nieminen, finalist in 2001 and 2006 and playing the event for the 12th consecutive year.

The 73rd-ranked Finn will compete in his second quarterfinal in a month after Bangkok, facing one of two Germans, Tobias Kamke or qualifier Sebastian Rieschick.

Nieminen took victory with 22 winners and a dozen unforced errors, breaking Wawrinka three times. The Swiss fired 24 winners but annulled the effort with 21 errors.

Wawrinka had been bidding for his eighth quarterfinal of the season.

Nieminen, once ranked 13th, had lost his previous nine matches against Top 20 players.

The Finn claimed victory after double faulting on the first of three match points but coming good on his third chance as Wawrinka netted a backhand.

Dimitrov, a 20-year-old tipped for a top career, admitted to a lapse against Chela after leading a set and 2-0. "I started struggling a bit and he raised his game," said the Bulgarian ranked 70th after getting back on track.

Dimitrov will next face Canadian sixth seed Milos Raonic. "It will be a great match, I know him well and will have to be on my game."

In Moscow, Marion Bartoli moved a step closer to securing the last remaining spot in the season-ending WTA Championships with a 6-1, 6-1 thrashing of Russia's Ksenia Pervak in the Kremlin Cup second round on Thursday.

After Poland's Agnieszka Radwanska, the only other player with a chance of making next week's championships, was knocked out on Wednesday, the third seed must win in Moscow to make sure of her place in the eight-player field.

"I understand the importance but I try not to think about it," Bartoli told reporters of her chances of reaching Istanbul.

"I will keep fighting for every point in every match," added the Frenchwoman, who will face Elena Vesnina in Friday's quarter-finals after the unseeded Russian eliminated compatriot Ekaterina Ivanova 6-3, 6-4.

Second seed Radwanska lost to unseeded Czech Lucie Safarova in the second round n Wednesday.

If she beats Vesnina, Bartoli could meet top seed Vera Zvonareva in Saturday's semi-finals.

On Friday, world number five Zvonareva, who has already booked her ticket to Turkey, takes on eighth-seeded Slovakian Dominika Cibulkova, who beat Czech Klara Zakopalova 7-6, 6-2.

Bartoli beat US Open champion Samantha Stosur in the Japan Open final on Sunday for her second title of the year.

"I'm satisfied with the season, which I'm sure to finish in the top 10," the world number nine said. "Even getting to Istanbul as an alternate is a big achievement."