Lame. Rafa just retired against Kolya after losing the first set 61. Looks to be a problem with his right thigh.
UPDATED: More on Rafa's injury
Nadal had received a lengthy massage treatment on his right thigh at 4-1 down to try and loosen the muscles around his right knee but was unable to start the second set.
"When I push with the right leg all the time the knee wasn't there, the knee is going down," Nadal said. "I felt a sharp, acute pain."
The Spaniard felt nagging knee pains earlier this week, and it got worse Friday morning.
"Today when I woke up I felt it a lot. I try to practice but still feel it," Nadal said. "Later I went the doctor and the doctor gave me some anti-inflammatories."
Nadal said he has never had a similar injury and that he needs further tests before he decides whether to play the season-ending Masters Cup, which begins Nov. 9 in Shanghai.
"We are going to have the tests and everything," Nadal said. "Hopefully it's going to be fine for Shanghai, but you never know."