London - Tomas Berdych remains in the hunt for a place in the semi-finals of the ATP Tour Finals after the Czech fifth seed defeated France's Jo-Wilfried Tsonga 7-5, 3-6, 6-1 at London's O2 Arena on Wednesday.
Berdych, who lost his opening Group A fixture against Andy Murray, now has to beat world number one Novak Djokovic on Friday to book his place in the last four of the prestigious season-ending event.
The former Wimbledon finalist's victory also means Djokovic isn't certain to qualify yet even though the Serb maintained his 100 percent record with a win over Murray earlier on Wednesday.
Tsonga isn't definitely eliminated but he would need to beat Murray in straight sets and hope Berdych loses by the same margin against Djokovic to advance.
"It was important to win and now I'm looking forward to the next match," Berdych said.
"I tried to just focus on myself and remind myself I had won the recent matches between us.
"I was a bit surprised with the score in the final set but not how hard I had to work for it. I played well and finished it well."
Berdych had beaten Tsonga in both of their meetings this year, including the final of the Stockholm Open, and the 27-year-old was a deserved winner again after a blistering finish.
Tsonga hasn't defeated a top-eight ranked player this year and once again the flamboyant Frenchman was too inconsistent on the big points.
Berdych had a chance to take control of the first set when he earned three break points in the seventh game, but Tsonga saved all three with a series of booming serves and powerful forehands.
Tsonga didn't make the most of his escape though as a series of wayward groundstrokes gifted Berdych the first break at 6-5 and the Czech gleefully seized the chance to serve out the set with an ace.
Berdych saved two break points at 1-2 in the second set, yet Tsonga was beginning to find some momentum and he pressured the Czech into one more mistake to move 3-1 ahead.
Tsonga briefly wobbled when he served for the set, giving Berdych a break point, but he held on to send the match to a decider.
Berdych was under pressure again in the first game of the final set, this time digging deep to save two break points, and he made the most of his reprieve with a break for a 3-1 lead.
Suddenly the tide had turned back in Berdych's favour and he sealed the win in emphatic fashion with a second break.