Sky Sports analyst Barry Cowan has tipped American Jack Sock to beat Bulgaria's Grigor Dimitrov at the Nitto ATP Finals.
Rolex Paris Masters champion Sock and Cincinnati Masters winner Dimitrov reached the semi-final in their debuts at The O2 Arena.
Sock, who lost to Swiss Roger Federer in his opener, beat Marin Cilic and Alexander Zverev to reach the semi-finals.
On the other side, Dimitrov comfortably cruised past Round Robin stage without a loss.
The head-to-head between the two stands at 3-1 in Sock's favor.
"I've gone for Sock," said Cowan. "On big points, he's fearless and has been playing a brand of tennis this week which is suited to these conditions. He can serve and volley, use the sliced backhand, and his forehand is huge.
"A match like this comes down to a little bit of belief. This must be of their wildest dreams being in the semi-finals of the ATP Finals.
"With everything that has gone Sock's way in the last couple of weeks, it's all dropped into place nicely. He was 5-1 down in the deciding set against Kyle Edmund in Paris, but he came through those moments to win the title - that only makes you stronger, mentally.
"It looks like a three-setter to me, but Sock to win."
Andy Murray's coach Jamie Delgado is also a believer in Sock.
"I'm going to call a bit of an upset and go with Sock to win the match," Delgado said.
"Dimitrov will be in the strange position of being the favorite, so the mentality of it will be slightly different."