Del Potro stunned, Isner through at Delray Beach

Juan Martin del Potro was stunned in the Delray Beach Open quarter-finals, while John Isner moved into the last four on Friday.

Del Potro's first tournament back from a knee injury was ended by Mackenzie McDonald, who upset the Argentine top seed 6-4 3-6 7-6 (7-5).

The 2011 champion was unable to take either of his two break-point chances in the final set, edged by McDonald after two hours, 19 minutes.

McDonald will meet Radu Albot, who surprised fourth seed Steve Johnson 1-6 6-3 7-6 (7-5).

Isner made it seven wins in eight meetings with Adrian Mannarino thanks to a 7-6 (7-2) 6-4 victory.

Semi-final bound! @JohnIsner is into the final four of the #DBOpen after a 7-6(2), 6-4 win over A. Mannarino. Next up for the No. 2 seed: Dan Evans... : Andrew Patron/@DelrayBeachOpen pic.twitter.com/nKYnAlPd1R

— USTA (@usta) February 22, 2019

The American will meet Dan Evans, the British qualifier having upset Italian sixth seed Andreas Seppi 6-4 6-4.

At the Rio Open, Pablo Cuevas remained on track to become the first man to win the ATP 500 event twice.

The Uruguayan 2016 champion overcame a second-set blip to get past Albert Ramos-Vinolas 6-3 3-6 6-3.

Vitória e vaga na semi para @PabloCuevas22, que elimina Ramos-Viñolas por 6/3 3/6 6/3. Por um lugar na final, o campeão de 2016 duela neste sábado com Auger-Aliassime. #RioOpen pic.twitter.com/jw8hoNJnVG

— Rio Open (@RioOpenOficial) February 23, 2019

Awaiting him in the semi-finals is Felix Auger-Aliassime, the 18-year-old Canadian having claimed a 6-4 6-3 win over Jaume Munar.

The other last-four clash will be between Laslo Djere and Aljaz Bedene, who continued their runs.

Djere, who stunned Dominic Thiem in the first round, beat qualifier Casper Ruud 6-4 7-5.

Bedene eliminated third seed Marco Cecchinato in his opener and moved into the semi-finals courtesy of a 4-6 6-2 6-3 win over Hugo Dellien.