Swiss star Stan Wawrinka needed only 37 minutes to place himself in the quarter-finals of the Geneva Open after his rival, Brazilian Rogerio Dutra Silva, retired at 5-2 in the opening set.
The Sao Paulo player suffered a massive fall in the 26th minute and had to be treated for a problem with his right ankle.
Realising his opponent was injured, Wawrinka did not hesitate to cross to the other side of the net and attend to Dutra on the ground until the Brazilian was transferred to his chair.
The injured player then endured a few minutes on the court, but in the end decided that it was dangerous to continue.
Wawrinka will face American Sam Querrey in the quarter-finals scheduled for Thursday.
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Querrey cruised into the quarters with a 6-2 6-3 win over Croatian qualifier Franko Skugor and was joined by fellow American, fifth seed Steve Johnson, who blitzed Horacio Zeballos 6-1 6-3.
It wasn't such a great day for Rome Masters semi-finalist John Isner, the powerful American conquered for the second week straight by a Zverev.
However this time it was older brother Mischa who did the damage with a 6-4 6-7 (7-5) 6-3 victory to move into a quarter-final against Johnson.
