3 times Rafael Nadal retired from a Grand Slam match due to injury

#3 US Open 2018

Del Potro (left) and Nadal talk after Rafa retired from the semi-finals of US Open 2018

Nadal has never defended a Grand Slam title outside of the clay of Roland Garros. The 32-year-old had a golden opportunity to change this stat in the US Open 2018. But the Spaniard retired in the semi-finals at the end of the second set against Juan Martin Del Potro.

Nadal was struggling because of a knee problem as he needed a medical attention twice in the match. The Argentine was leading 7-6(3), 6-2 when Nadal quit but the 17-time Grand Slam champion was struggling because of the knee injury right from the first set.

The World No. 1 even had problems in his right knee against Karen Khachanov in the third round. It has caused Nadal a lot of problems in his career and so it did on Friday at the Flushing Meadows, ending the run for an 18th Grand Slam title for Nadal.

Nadal said " It was difficult for me to keep playing. I was in too much pain. I hate retiring -- but to stay one more set out there playing like that is too much for me."