London - Six-time champion Roger Federer will face rising star Alexander Zverev at the ATP Tour Finals in London after they were placed in the same group on Wednesday while Rafael Nadal headlines the other section.
Federer, 36, looking to crown a remarkable year in which he has lost just four matches following a return from a lengthy lay-off, will also face former US Open champion Marin Cilic and American Jack Sock in the Boris Becker group.
Nadal's opponents in the Pete Sampras group are Dominic Thiem, Grigor Dimitrov and David Goffin, with the Spanish world number one looking to win his first ATP Finals trophy.
Nadal pulled out of last week's Paris Masters before his quarter-final with a knee injury, placing his participation in London in doubt.
Federer has won seven titles this season including the Australian Open and Wimbledon, but lost out on the year-end number one ranking to his long-time rival Nadal.
Germany's Zverev, 20, has rocketed to third in the world rankings after an impressive year in which he has won five titles, including beating Federer in the final of the Rogers Cup Masters event in Montreal.
The ATP Finals, starting on Sunday, are the year-end climax to the men's professional tennis season, featuring the world's best eight qualified singles players and doubles teams.
Players compete for rankings points throughout the season in a bid to earn one of the eight coveted berths.
Played using a round-robin format at The O2 in London, each participant plays three matches as they compete for a berth in the knockout semi-finals.
Group draw: (world ranking in parentheses)
Pete Sampras Group
(2) Roger Federer - Switzerland
(3) Alexander Zverev - Germany
(5) Marin Cilic - Croatia
(9) Jack Sock - USA
Boris Becker Group
(1) Rafael Nadal - Spain
(4) Dominic Thiem - Austria
(6) Grigor Dimitrov - Bulgaria
(8) David Goffin - Belgium