By Martyn Herman
LONDON (Reuters) - Dominic Thiem stayed very much in the mix at the ATP World Tour Finals with a 6-3 1-6 6-4 victory over mercurial Frenchman Gael Monfils at the O2 Arena on Tuesday.
The Austrian weathered a mid-match storm when an apparently injured Monfils burst into life with some audacious tennis and stayed solid to claim his maiden victory at the season-ending event.
It means the 23-year-old will go into his final Ivan Lendl group match against Milos Raonic on Thursday with a chance of reaching the semi-finals.
Beaten by Novak Djokovic in his opening match, Thiem used his baseline power to boss the first set against an erratic opponent also making his debut at the event.
But the contest took a wild turn as Monfils changed tactics and began to let rip with some fearsome groudstrokes, levelling the match in what seemed the blink of an eye.
Thiem stuck to his game plan, however, and kept his nose ahead in a fiercely contested third set.
The dexterous Monfils saved three break points at 3-4 but Thiem sealed his maiden victory at the event when Monfils crumbled at 4-5 and served two double-faults.
Monfils also lost to Canada's Milos Raonic in his opening match on Sunday and was hobbling at times, putting his continued participation in some doubt.
Djokovic and Raonic meet later on Tuesday with both looking to claim their second group victory.
Serbian Djokovic, bidding to reclaim the world number one ranking, leads 7-0 in their previous matches.
(Editing by Ed Osmond)