David Goffin advanced into the semi-finals of the ATP finals after a comfortable victory over Dominic Thiem in London.
Thiem was unable to get going on Friday and he could only produce a below-par performance.
He started well and raced into a 3-0 lead but Belgian Goffin showed plenty of heart to win 12 of the next 14 games.
Constant errors gifted Goffin the first set and he then powered home to win 6-4 6-1 in the end as he booked his place in the semis against Roger Federer.
Goffin admits it will be a tough encounter and he had sympathy for Thiem in defeat.
He told reporters: "It will be a tough match, so nice to play a semi against him. 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."
tagged in Roger Federer