Milos Raonic and Karen Khachanov were the two seeds to exit in the Dubai Tennis Championships first round on Monday while Roger Federer advanced to the last 16.
Federer is a seven-time champion at this ATP 500 tournament and the Swiss is one title away from bringing up 100 Tour-level crowns.
The 20-time grand slam winner dropped the second set against Philipp Kohlschreiber but eased through the decider en route to a 6-4 3-6 6-1 victory that extends his perfect record over the German to 14-0.
Federer's opponent in the second round will be 2017 runner-up Fernando Verdasco, who came from a set down to defeat Thomas Fabbiano 3-6 6-3 6-2.
Fourth seed Khachanov, meanwhile, was thumped 6-4 6-1 by Nikoloz Basilashvili, who broke right at the end of the first set and then twice more in the second to book a meeting with defending champion Roberto Bautista Agut, who overcame Ramkumar Ramanathan 6-4 6-3.
Raonic, seeded seventh in Dubai, was ousted 6-4 5-7 6-4 by Jan-Lennard Struff. The German is through to face Marton Fucsovics, a 6-1 7-6 (7-5) conqueror of Damir Dzumhur.