Rafael Nadal will have the chance to test his match fitness when he faces South Africa's Kevin Anderson in Abu Dhabi.
Anderson, ranked sixth, defeated Hyeon Chung of South Korea 6-7 (4-7) 6-2 6-1 in the quarter-finals of the Mubadala World Tennis Championship.
A right knee injury forced world No.2 Nadal to retire from his US Open semi-final in early September - his last competitive match - and the 32-year-old Spaniard had ankle surgery at the start of November.
On Thursday, Nadal said he was confident he can be fit in time for the Australian Open, which starts on January 14.
World No.1 Novak Djokovic will face Karen Khachanov in the other semi-final in Abu Dhabi after the Russian beat Austria's Dominic Thiem 7-6 (7-3) 6-3.
In a one-off match, Venus Williams prevailed over younger sister Serena 4-6 6-3 10-8.
Serena, 37, broke 38-year-old Venus' serve twice to win the first set but faltered in the second, dropping three service games on the way to losing 6-3.
The contest went to a super tie-break.
While Venus dropped her opening serve, she outlasted Serena to win 10-8.
"Serena said I was playing well. I think we can only go up from here and that's our plan," Venus said after defeating the winner of 23 Grand Slam titles.
"It was really fun and so good to see everyone come out to support myself and Venus. It was really fun out here," Serena said.
