| BELGRADE, Sept 15
BELGRADE, Sept 15 Novak Djokovic is not certain to play Friday's opening singles rubber in Serbia's Davis Cup semi-final against Argentina in the Belgrade Arena, the world number one said on Thursday.
Djokovic, who won his first U.S. Open title in New York on Monday, arrived in Belgrade on Thursday and went straight to the venue to practice after missing the draw which pitted him against David Nalbandian in the first match.
"It's no secret that I am physically and mentally exhausted but it's been a very successful U.S. open tour for me winning the fourth grand slam in my career and the third this year," Djokovic told reporters.
"I am happy to be back and to be able to celebrate this title with my family and my people and to play again in front of Serbians.
"There is a possibility (that I will miss the opening singles rubber) and there is the possibility that I will play, for now we've agreed that I play so we'll see how I feel after hitting some balls in practice.
"I'll have a conversation with my team tonight and tomorrow, it doesn't just depend on me, it depends on the whole team because this a team effort and not just about one individual."
Serbia team captain Bogdan Obradovic said he expected fans to turn up in numbers and support the 2010 winners of the competition whether Djokovic plays or not.
"No matter who is on the court, we expect the fans to throng the Belgrade Arena's terraces an hour before the tie starts in order to create the right kind of atmosphere," Obradovic told a news conference after the draw.
Janko Tipsarevic, who lost to compatriot Djokovic in a brutal U.S. Open quarter-final clash when he had to retire with a thigh injury, takes on Juan Martin Del Potro in Friday's second singles.
Serbia's Nenad Zimonjic and Viktor Troicki -- who will stand in for Djokovic if the world number one fails to recover from jetlag and fatigue -- meet Juan Ignacio Chela and Juan Monaco in Saturday's doubles, with the reverse singles on Sunday.
The Serbs won their first Davis Cup title last year with a 3-2 win over France in the Belgrade Arena, where they are undefeated as a team while Djokovic, who has only lost two matches on the ATP tour this year, also has a perfect singles record.
The 24-year old Belgrader, who also won the 2011 Australian Open and Wimbledon titles on the way to leaping over Roger Federer and Rafael Nadal to the pinnacle of the rankings, said the Davis Cup victory had triggered his personal success.
"I love the Davis Cup, it's a very unique competition where you get to represent your country and I love playing for my country," he said.
"The schedule is difficult that's for sure and we will try to make a better schedule for us in the future because most of the top players play a lot and it's difficult to play in every single Davis Cup.
"But here I am and it's been a very similar situation like last year but winning the Davis Cup trophy in 2010 gave me wings, it gave me a lot of energy."
Djokovic acknowledged he was taken aback by his success in 2011, in which he also won five Master Series events, the Serbia Open and the Dubai Championships.
"It seemed very unreal for me winning three grand slams in a year and so many matches in a row but the hard work that I put in the last couple of years is paying off now," he said.
"I just try to go on as much as I can, I try to think positive and take it one match at a time."