Grigor Dimitrov and Nick Kyrgios were among the first-round winners at the Madrid Open as Jack Sock bowed out.
Dimitrov, the 12th seed, was tested before getting past German Philipp Kohlschreiber 7-6 (9-7) 6-4 on Monday.
The Bulgarian advanced in one hour, 48 minutes on what was a relatively good day for the seeds in Spain.
Despite battling a groin injury, Kyrgios claimed a 7-6 (7-1) 6-4 win over Marcos Baghdatis.
The Australian, a quarter-finalist at the ATP 1000 event last year, sent down 14 aces and did not face a break point.
Only two seeds departed on the clay, with Sock and Gael Monfils exiting.
Sock, who held an impressive 20-6 win-loss record this year heading into the event, was a shock 6-4 0-6 7-6 (7-4) loser to Nicolas Mahut.
In a rollercoaster all-French clash, Monfils went down to Gilles Simon 0-6 6-0 7-6 (7-0).
Czech 11th seed and 2012 runner-up Tomas Berdych encountered few problems on his way to a 6-4 6-4 win over qualifier Denis Istomin.
Jo-Wilfried Tsonga needed almost three hours to overcome Andrey Kuznetsov 7-6 (7-5) 6-7 (5-7) 7-5.
Meanwhile, Feliciano Lopez was too good for Ernesto Escobedo 6-4 6-4, David Ferrer beat Mikhail Kukushkin 2-6 7-6 (7-1) 6-4 and Florian Mayer claimed a 7-5 7-5 win over Marcel Granollers.
Pablo Cuevas battled past Thomaz Bellucci 7-6 (7-2) 4-6 7-6 (8-6), Jared Donaldson recorded a 7-5 6-3 win against Adrian Mannarino and Robin Haase beat Daniel Evans 7-5 6-2.
Marius Copil saved two match points to win a battle of wildcards 7-6 (8-6) 4-6 7-6 (11-9) over Guillermo Garcia-Lopez.