Tsitsipas is the youngest finalist since Juan Martin del Potro in 2009, while it will be just the third final since 2002 not to include Federer, Novak Djokovic or Rafael Nadal.Federer was supreme in beating great rival Djokovic to reach the semi-finals on Thursday but was well below his best on this occasion and was left rueing a host of missed opportunities on crucial points.The 17-year age gap between the two players is the biggest in the history of the season-ending championships.With the London crowd heavily in favour of Federer, Tsitsipas played the better tennis, particularly on the big points. The Greek saved break point in the very first game before clinching Federer’s opening service game minutes later with a forehand winner.In total, Federer had six break points in the opening set but failed to take any as Tsitsipas held firm and the 20-time Grand Slam champion gifted points with errors.Serving for the set at 5-3, Tsitsipas fought off two of those break points but saw six set points of his own come and go in a marathon game before clinching the opener on his seventh.Federer’s errors gave his opponent an further early break in the second set, only for the Swiss to finally convert a break point a game later at the 10th attempt.But, after the crowd roared in hope of a comeback, Tsitsipas crunched another forehand winner to seal Federer’s service game. Typically, Federer had two more break points when Tsitsipas served for the match but the Greek closed out the win with some big deliveries.Tsitsipas was aged just five when Federer won his first Wimbledon title in 2003 and said it was a “dream come true” to beat him in London.“I grew up watching Roger here at the ATP Finals and Wimbledon and other finals,” he said. “I wished one day I could face him and today I’m here living the dream.”He was already the youngest player to have recorded wins against Federer, Djokovic and Rafael Nadal but this victory strengthens further his standing as one of the best young players in the game.Share this:FacebookRedditTwitterPrintPinterestEmailWhatsAppSkypeLinkedInTumblrPocketTelegram Tsitsipas Stefanos Tsitsipas will play Dominic Thiem for the title at the ATP Finals today after beating six-time champion Roger Federer in London. The Greek, making his debut at the event aged just 21, won 6-3 6-4.Swiss Federer, 38, was aiming for a record-extending seventh title but was undone by the nerveless Tsitsipas, just as he was at January’s Australian Open.Later, Austrian fifth seed Thiem saw off defending champion Alexander Zverev 7-5 6-3. Thiem, 26, and Tsitsipas will be competing in their first final at the season-ending tournament and aiming for the biggest title of their careers.