Cincinnati: Novak Djokovic was paying the price for sustained excellence on Sunday, but after retiring injured from the Cincinnati Masters final the weary and aching world No. 1 vowed to bounce back at the US Open.
Djokovic, battling fatigue and a painful right shoulder that hindered his serve and forehand, called it quits while trailing Scotland's Andy Murray 6-4, 3-0.
It was just the second defeat of the season for the Serbian, who arrived in Cincinnati after capturing the Montreal Masters the previous week and was trying to complete a third set of back-to-back Masters titles after his Indian Wells-Miami hardcourt titles were followed by victories at Madrid and Rome.
In all he has won nine titles this season, including the Australian Open and Wimbledon.
His victory at the All England Club saw him rise to the top of the rankings, but his spectacular success has a downside.
"I've played so many matches this year," Djokovic said. "I've been winning a lot and reaching the final stages of each event that I've participated in.
"Considering the schedule that is very busy in tennis, it's kind of normal to expect that at some stage you are exhausted. But as I said, I am confident that I can recover and be ready for US Open."
Djokovic's only prior defeat this season was to Roger Federer in the semi-finals of the French Open.
That halted his season-opening winning streak at 41 matches -- one shy of tying John McEnroe's 1984 record of a 42-match winning start to a season.
Since then Djokovic had won 16 straight matches, but even in Montreal he was feeling a niggling discomfort in his shoulder.
"The major issue was shoulder," he confirmed. "Generally I was quite exhausted playing many matches, but the exhaustion is not the reason.
"The reason is shoulder pain. I just could not serve. I served an average 90 miles per hour the first serve, and I could not play forehands... Running forehand mostly, or when I'm on the stretch.
"Of course I'm not saying if I was 100 percent that I would certainly win because Andy is a great player. But I am sure that we will have a better match."
Now the state of Djokovic's shoulder will become a major topic as the US Open looms. He said he hadn't pursued an MRI exam.
"I didn't have time," he said. "I was playing every day."
But Djokovic said the stresses of the season were the same for all top players. Even plans to amend the calendar next season won't help that much.
"There has been certain changes from next year -- the year will be two weeks shorter.
"But still, the intensity is going to be the same, if not tougher. But it's the same for everybody. We just have to get used to it and adjust."