Rafael Nadal moved through at the US Open as David Ferrer's final grand slam match ended with an injury on Monday.
Nadal, the defending champion in New York, was leading the first-round match 6-3 3-4 when Ferrer retired due to a suspected calf injury.
The 2013 French Open runner-up, an apologetic Ferrer – who lost that final to Nadal – confirmed the exit marked his last major appearance.
"I have really good memories here at the US Open," Ferrer said. "This is the last grand slam of my career and I am so sorry because I can't finish the match."
Nadal, who had won 24 of his previous 30 meetings with Ferrer, was always a favourite against his fellow Spaniard.
A pair of breaks in the first set saw 17-time grand slam champion and world number one Nadal grab the opener.
It was Ferrer who broke twice in the second set, but the 36-year-old was unable to continue after one hour and 23 minutes.
Nadal will face Canadian Vasek Pospisil in the second round.