Portugal have announced Deco will have a scan on Tuesday to assess the damage to his right hip.
The midfielder was ruled out of Monday's 7-0 demolition of North Korea after aggravating his hip in training.
The 32-year-old is to undergo an MRI scan to see whether he will be fit for Portugal's final Group G game against Brazil.
The Portuguese football federation say the Chelsea schemer is "still in pain in his right hip which is preventing him from training normally."
Brazilian-born Deco will be desperate to be fit for the Durban clash but his place in Carlos Queiroz's side is under threat after a poor performance against the Ivory Coast.
His replacement, Tiago, scored twice and had provided an assist in the rout against North Korea.