Dominic Thiem fought past world number one Novak Djokovic to reach Sunday’s title-decider at the ATP Finals.
Djokovic saved five match points in a cagey affair but the Austrian recovered from a poor second-set tie-break to win 7-5 6-7 (10-12) 7-6 (7-5) in London.
The Serb led 4-0 in the deciding tie-break but Thiem, trusting in his big hitting, was able to outmuscle Djokovic and claim a fine win at the O2 Arena.
Thiem will play Rafael Nadal or Daniil Medvedev in the final.
Spanish world number two Nadal, who has never won the season-ending showpiece, plays the Russian at 20:00 GMT on Saturday.
Thiem’s increased confidence, built in a year where he won his first Grand Slam title at the US Open, was enough to enable him to edge past Djokovic in a tight third set.
He covered his face in delight after putting away a forehand winner that secured victory after two hours 57 minutes.