Djokovic said he realised his compatriot was in trouble after the first two hotly-contested tiebreaker sets. The top seed won the first tie-break 7-2, and lost the second 7-3.
“I sensed when I made a break in the third set that he lost a lot of pace on his first serve and was not able to move so well,” the Serb added.
Djokovic also gave onlookers a scare when he doubled over and called for the trainer after making a spectacular sliding forehand winner in the first game of the fourth set.
After getting the big toe on his left foot treated and bandaged, Djokovic went back to business before the 20th-seeded Tipsarevic signalled he had had enough.
“My left toe is bleeding,” explained Australian Open and Wimbledon champion Djokovic. “These things happen all the time when you’re sliding like I do.”
Djokovic will meet the winner of Thursday’s night match between five-time Open winner Roger Federer and France’s Jo-Wilfried Tsonga.
[ < Volimo Nole > ] US Open 2011 #4: "It's both easier and harder"
