Djokovic, back at No. 2 in the world after his inspired run to the final at Flushing Meadows, will spearhead Serbia's challenge in Belgrade as they attempt to reach the final for the first time.
In the other semifinal in Lyon, Argentina will have to beat nine-times Davis Cup champions France for the first time if they are to reach the end-of-season showpiece — their hopes resting heavily on the shoulders of a resurgent David Nalbandian.
France are without the injured Jo-Wilfried Tsonga while Argentina's 2009 US Open champion Juan Martin del Potro has been sidelined for almost the entire year with a wrist injury.
Fiercely patriotic, Djokovic will have to quickly recharge for what promises to be a difficult task for the Serbs in the 17,000-capacity Belgrade Arena that will be packed to the rafters when the tie begins on Friday.
That raucous home support will help Djokovic who will still be feeling the effects of the effort he expended to beat Roger Federer in an epic five-set semifinal in New York before succumbing to Nadal in a rain-delayed title match late on Monday.
"It's hard to recuperate from the exertions of a grand slam then travel east to make up a six-hour time difference," Niki Pilic, who lead Croatia to the 2005 title and is now an adviser to the Serb team, told Serb media on Tuesday.
"Nevertheless we are confident that Novak will be up to the task because when you have the No. 2 in the world in your team there is no Plan B. He is the backbone of the team." Viktor Troicki, who almost beat Djokovic in the first round of the US Open, is expected to be Serbia's second singles player with world number three doubles player Nenad Zimonjic likely to partner Janko Tipsarevic in Saturday's doubles.
Unlike Djokovic, Czech number one Tomas Berdych will have no worries about fatigue, having been ditched out of the US Open early.
The Wimbledon runner-up will share the singles workload with Radek Stepanek who said he is relishing the prospect of the firecracker atmosphere that will await the visitors in Belgrade.
"Playing them in Serbia will definitely be tough because their fans will be standing behind them," Stepanek told the Davis Cup website (www.daviscup.com).
"They are playing in the World Group (semifinals) for the first time so definitely the people are pumped about it. But we have a great team and we believe in ourselves.
"We've been underdogs so many times, the same as we will be in Serbia, and we will try to use it to our advantage and do what we've done for the last two years." Having beaten reigning champions Spain in the quarter-finals, France will be favorites to reach the final for the first time since 2002 when they lost to Russia in Bercy.
Team captain Guy Forget hopes Gael Monfils can step up in the absence of Tsonga while Gilles Simon or Richard Gasquet will probably fill the second singles spot, leaving Michael Llodra to provide the doubles expertise.
"The absence of Tsonga is not worrying me because at the US Open I saw Gael playing well and Richard coming back close to his best level," Forget said.
Argentina's team arrived in Lyon last Friday after the doubles duo of Horacio Zeballos and Eduardo Schwank lost in the US Open semifinals.
"It was a good idea to have landed several days earlier than usual," captain Modesto "Tito" Vazquez said. "The group are in good spirits." Nalbandian, who was devastating in beating Nikolay Davydenko and Mikhail Youzhny in the 3-2 quarter-final win over Russia, is expected to have shrugged off an ankle injury in time for Friday's start. Juan Monaco is Argentina's second singles pick having missed the wins over Sweden and Russia.
