David Goffin set up an ATP Finals last-four clash with Roger Federer by overcoming a slow start to beat Dominic Thiem in straight sets.
With both men having taken one win from their opening two group matches, their meeting at the O2 Arena served as a winner-takes-all contest.
It initially looked as if Thiem was going to be the one to take control as he forged a 3-0 lead in the first set, however, Goffin wrestled the momentum away from the Austrian and never looked back.
The Belgian needed just an hour and 11 minutes to complete a 6-4 6-1 victory and book a Saturday showdown with Federer, who he has never beaten in six meetings.
Thiem quickly seized the initiative as he broke to love in the second game, Goffin sending a forehand long, and had little issue consolidating that break to seemingly move into a position of command.
However, Goffin promptly broke back in the fifth as Thiem meekly surrendered a service game without winning a point, and then went a break up when his opponent blasted a forehand wide.
A stunning forehand pass secured the set for Goffin and, after Thiem received treatment on his left knee during the interval, the world number eight continued in the ascendancy by breaking in the third game.
Thiem fired long to spurn a break-back opportunity in the subsequent game and an errant backhand handed Goffin the double break shortly after.
Goffin needed 10 minutes to hold for 5-1 as Thiem displayed some signs of resistance, only to see four more break points go begging.
And a frustrating match for the world number four came to a fitting end as Goffin wrapped things up by giving a poor second serve the appropriate treatment with a return to which Thiem could not respond to clinch second spot in Group Pete Sampras.
Goffin  bt Thiem  6-4 6-1
Goffin - 10/20
Thiem - 11/27
BREAK POINTS WON
Goffin - 5/7
Thiem - 1/6
FIRST SERVE PERCENTAGE
Goffin - 66
Thiem - 43
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Goffin - 74/45
Thiem - 67/36
Goffin - 62
Thiem - 45