DELRAY BEACH, Fla. -- Top-seeded Juan Martin del Potro never faced a break point and won his second-round match Thursday night at the Delray Beach Open, beating American Reilly Opelka 6-4, 6-4.
Del Potro overcame 18 aces by Opelka and will next face American Mackenzie McDonald, who beat Guillermo Garcia-Lopez 7-5, 6-4.
Del Potro is playing his first event after missing four months because of a knee injury. He won the tournament in 2011.
No. 4 Steve Johnson reached the third round by beating Paolo Lorenzi 7-5, 7-5. Nick Kyrgios lost to Radu Albot 6-2, 3-6, 6-3.