Novak Djokovic's participation in the opening rubber of the Davis Cup semi-final against Argentina on Friday has been thrown into doubt as the Serbian star arrives home just days after lifting the US Open title.
The world number one was drawn on Thursday to take on 74th-ranked David Nalbandian in the opening match here. But the 24-year-old will arrive in Belgrade on Thursday just three days after beating Spaniard Rafael Nadal in the US Open final.
"Novak arrives today and we'll see at what point he will be ready to play," teammate Viktor Troicki said. "In any case I'll be ready and will fight for each point to help Serbia to victory," added the world number 16.
Coach Bogdan Obradovic can change his team up to an hour before the tie as the reigning champions bid a second consecutive final.
Davis Cup veteran Nalbandian, 29, faces a potentially tough task against Djokovic, who has a 64-2 win-loss record in 2011 including a remarkable three Grand Slam titles.
The Serb leads 4-1 in previous meetings with Nalbaldian's last win coming on hardcourt in Madrid four years ago.
US Open quarter-finalist Janko Tipsarevic has been drawn against 2009 US Open champion Juan Martin del Potro in the second rubber on the hardcourt Belgrade Arena.
Tipsarevic will then team up with doubles specialist Nenad Zimonjic against Juan Ignacio Chela and Juan Monaco on Saturday before Sunday's reverse singles.
Friday (from 13:00 GMT):
Novak Djokovic (SRB) v David Nalbandian (ARG)
Janko Tipsarevic (SRB) v Juan Martin Del Potro (ARG)
Saturday (from 13:00 GMT):
Janko Tipsarevic/Nenad Zimonjic (SRB) v Juan Ignacio Chela/Juan Monaco (ARG)
Sunday (from 12:00 GMT)
Novak Djokovic (SRB) v Juan Martin Del Potro (ARG)
Janko Tipsarevic (SRB) v David Nalbandian (ARG)