Derby County club captain Shaun Barker is to spend two weeks in America as he steps up his rehabilitation following his career-threatening knee injury.
Barker suffered a horrendous injury in March 2012, dislocating his kneecap and rupturing medial ligaments and anterior and posterior cruciate ligaments.
The 31-year-old defender has started light training exercises with a ball.
But head physiotherapist Neil Sullivan said although Barker is making progress he is still "some way off" a return.
It was originally hoped Barker would be nearing a return to action by now, and the length of time the centre-half has spent on the sidelines has cast doubt on whether he will be able to make a full recovery.
But there has been no return date set for when he will start running again and Barker is to fly to Philadelphia on 10 November to spend a fortnight with sports rehabilitation specialist Bill Knowles.
Barker told the club website: "I've progressed in recent months to put heavier weight on my knee and I think my time in America will be very valuable."
Sullivan added: "Bill Knowles is someone I invited to the training centre earlier this year to spend two days training our medical team in his methods and practices, and to meet Shaun to discuss his rehabilitation.
"For us to be able to call upon the best specialists in the world to give Shaun that extra boost is invaluable.
"We obviously want him to have the best chance possible of resuming his career and this trip to see Bill will help with that aim."