Goffin, the seventh seed, completed the line-up for the last four with an impressive 6-4 6-1 win against the fourth seed at the 02 Arena.

The 26-year-old Belgian's reward for beating Thiem is a semi-final meeting with Swiss maestro Roger Federer tomorrow.

"It will be a tough match, so nice to play a semi against him," said Goffin.

"It was a pity to play against Dominic, he is such a good friend and a nice guy, it's never easy to play against a friend.

"It was tough, I was focused, I knew I had to stay calm and be ready for a tough battle. 

"At the end I was happy with the way I managed the match.

"After the first match against Rafael I wasted so much energy, I was not ready for Grigor, but I had a good rest yesterday and was ready for today, and I hope I can do the same for the semi-finals."

Thiem began the contest brightly and quickly raced into a 3-0 first-set lead.

But Goffin gradually found his way back into the match and ended up winning 12 of the next 14 games.

The Belgian broke back in the fifth game after a double fault from the Austrian and built on that momentum to take the opener.

The second set proved to be a one-sided affair as Goffin dominated, dropping just one game on his way to securing a place in the semi-finals.

Grigor Dmitrov of Bulgaria, who had already qualified for the semi-finals, swept aside Spain's Pablo Carreño Busta 6-1, 6-1 in the final group stage match of the tournament.

Dmitrov is due to take on American Jack Sock in the last four.