Djokovic and the rest of his Serbian team are unhappy that a clay surface has been laid on top of an indoors parquet floor.
"This is definitely the worst court we have ever played on," he said. "We're all putting our health at stake here.
"How is it possible that a clay court can be solid and can be a successful, playable court if it's built on parquet? We tried to slide a few times ... but our feet stayed under ground."
Djokovic, back in the team for the first time since September 2011, also said he was still feeling jetlagged after beating Britain's Andy Murray at the Australian Open final on Sunday.
"I am not fully recovered and I'm doing my best in order to prepare myself for tomorrow," he said.
Serbia are without injured world number nine Janko Tipsarevic but are still favourites to progress against Belgium who are led by world number 50 David Goffin and 127th-ranked Olivier Rochus.
The other singles player for the Serbs is world number 39 Viktor Troicki.