Kyrgios crashes out of Delray Beach Open

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Del Potro, playing his first tournament since October after a knee injury, broke once in each set to beat Reilly Opelka 6-4 6-4 in the second round.

The Argentine top seed, champion at the ATP 250 event in 2011, next faces Mackenzie McDonald, who overcame Guillermo Garcia-Lopez 7-5 6-4.

However, Kyrgios bowed out with a 6-2 3-6 6-3 loss to Radu Albot, who will meet Steve Johnson after the fourth seed's 7-5 7-5 victory over Paolo Lorenzi.

At the Rio Open, the last of the remaining seeds – Joao Sousa – departed to leave the field wide open.

Sousa was beaten by qualifier Casper Ruud 6-3 3-6 6-4 in the second round to become the last of the eight seeds to exit.

Ruud will face Laslo Djere, who was too good for Taro Daniel 6-4 6-2 to add to his upset win over Dominic Thiem.

Pablo Cuevas and Albert Ramos-Vinolas will also meet after wins over Juan Ignacio Londero and Federico Delbonis respectively.