London, Nov 18 (IANS): Canada's Milos Raonic joined Serbian World No. 2 Novak Djokovic in the final four of the ATP World Tour tennis Finals by defeating Austria's Dominic Thiem 7-6 (7-5), 6-3 here.

In a battle of the two youngest players in this elite eight-man event, the 25-year-old Raonic used his massive serve to power past his 23-year-old opponent in an hour and a half on Thursday, reports Efe.

The fourth-ranked Canadian, who struck 14 aces and won 86 percent of his first-serve points and 62 percent of his second-serve points, did not face a single break point in the contest.

Thiem put up a strong fight in the first set, but went down a break early in the second and lost his serve one final time to bow out of that final Group Ivan Lendl round-robin match and the tournament.

With the win, Raonic advanced to the semifinals of tennis' year-end championship event for the first time and remains in contention to finish 2016 as the world's third-ranked player.

English former soccer great David Beckham, a big tennis fan, was in attendance at the match with his son Romeo.

Also on hand was American former tennis great John McEnroe, who has been working with Raonic in recent months and sat with the other members of his coaching team -- former Spanish star Carlos Moya and Italy's Riccardo Piatti -- during the match.

Had Thiem won Thursday night's contest, he would have become the youngest semifinalist at the year-end championships since Argentina's Juan Martin del Potro in 2009.

But Thiem lost convincingly, with Raonic having the edge in winners (31-17) and unforced errors (14-18).

The two players also played even in the rallies, with the big-serving Raonic not only getting a lot of easy points with his most potent weapon but also winning half of the points that lasted five shots or more.

Earlier on Thursday, Djokovic, who had already advanced to the semifinals by winning his first-two round-robin matches, remained perfect at this year's ATP World Tour Finals by routing Belgium's David Goffin -- a replacement for injured Frenchman Gael Monfils -- 6-1, 6-2 in just over an hour.

Djokovic is trying to earn the year-end No. 1 ranking for the fifth time in his career, but he is in a tight battle for the season-ending top spot with Britain's Andy Murray.

The remaining two semifinalists will be determined on Friday, when the top-ranked Murray takes on Swiss world No. 3 Stan Wawrinka and Japanese world No. 5 Kei Nishikori squares off against Croatian world No. 7 Marin Cilic in Group John McEnroe.