Roger Federer has been drawn alongside Alex Zverev, Marin Cilic and Jack Sock in the ATP World Tour Finals group stages.
Federer and Zverev are tied at two wins each in their ATP head-to-head record, with the German Tour Finals debutant winning their most recent meeting in Canada - which is also their only previous clash on a hard court.
The Swiss star and 19-time champion will also come up against Cilic, who he beat in this year's Wimbledon final, and Sock in the Pete Sampras Group.
Sock was the last man to qualify for the season-ending showpiece with his win in the Paris Masters and becomes the first American to compete in the tournament since Mardy Fish in 2011.
Rafael Nadal is still rated as doubtful for the Tour Finals, with fellow Spaniard Pablo Carreno Busta the first alternative should he withdraw, but he was included in the draw.
The world number one is in the Boris Becker Group alongside David Goffin, Grigor Dimitrov and Dominic Thiem.