QUEENSLAND captain Darren Lockyer remains at long odds to play in Wednesday's second State of Origin clash as he continues to battle knee pain.

The champion five-eighth trained for the first time since his NRL comeback eight days ago on Friday but lasted only 10 minutes in an opposed session on the Gold Coast.

Titans halfback Scott Prince was called into camp as cover for Lockyer, who also missed Origin I with his knee complaint.

The Maroons must decide by today whether to keep Prince in camp and rule Lockyer out or release the Gold Coast star for tomorrow night's clash with Melbourne and risk forcing him to back up for Origin 48 hours later.

Queensland assistant coach Neil Henry yesterday said Lockyer's fitness issue had become no clearer.

He said the 31-year-old remained in doubt to overcome the knee injury and help lead the Maroons in the must-win game at Suncorp Stadium.

"I think at this stage Darren is a 50-50 chance of playing," Henry said. "He did about 10 to 12 minutes of the opposed session with the Queensland [under]-18s yesterday and came straight off to apply ice to his knee."

Johnathan Thurston is training and is considered almost certain to play after a groin scare.

The Titans remain unclear over whether Prince will be released for their crucial clash with the front-running Storm.

Betting is suspended on the game until a decision is made.