Fulham boss Roy Hodgson has revealed that striker Andy Johnson has undergone an exploratory operation in a bid to solve his groin problem.

Johnson was missing from the Fulham side that drew 1-1 with Bolton on Saturday and Hodgson now fears that the former England international could be out for some time.

Johnson has been struggling with the injury since early October and despite intensive treatment, he has continued to suffer in pain, as Hodgson revealed.

"He had an operation on Saturday and I am waiting to hear what the results of that are," said Hodgson. "It is pretty much exploratory because he has tried so hard to get back.

"There have been days when we thought he has cracked it and got manageable pain but then the following day when he comes out to training, he does not have manageable pain.

"He is forced to go back inside again and that was the case on Friday and the day before. That has prompted us, after the numerous scans and alternative medicine, to operate and go into the area where he is suffering the pain in the hope of finding out what it is and put it right. I fear he will be out for some time."

While Johnson struggles to regain his fitness, Hodgson can soothe himself in the knowledge that he has probably rescued Damien Duff's career from going into freefall.

Duff's 75th-minute equaliser against Bolton was drilled home with his right foot and Hodgson is delighted with the form of the Republic of Ireland international since he rescued the 30-year-old from Newcastle for a fee reported to be in the region of £4million.

Hodgson was the manager of Blackburn between June 1997 and November 1998 and saw at first hand the enormous potential of the young winger, who moved to Chelsea for £17million in July 2003. Duff later joined Newcastle for £5m in July 2006, spending three years on Tyneside.

"I didn't follow him closely during those years he was at Newcastle because I was out of the country, all I know is when he left Chelsea to go to there for big money, he suffered quite a number of important injuries," said Hodgson.

"Whether suffering injuries is the same as losing your way is something I would contest. All I can say is that he is a better player than the one I worked with at Blackburn 12 years ago.

"I thought he was an outstanding talent then and a very good player. But I think he is a better one today.

"Perception is important in football. The perception that he had lost his way or the injuries had taken their toll - these type of things permeate the world of football. People listen to them, people in my position probably had the same perception "Oh no, forget him he is a man of the past," but luckily I was not prepared to do that.

"What I saw of him playing for Newcastle last year, I thought I saw in him what I'd always seen."

Bolton brought a run of three straight defeats to an end with Ivan Klasnic scoring a 34th-minute opener. Unfortunately, Gary Megson's side could not withstand a second-half onslaught from Fulham to earn their first win in four games

But Megson insists that Klasnic, who scored from close range, is still not the finished article in terms of being a fully-fledged Bolton player.

The striker, a direct replacement for the dropped Johan Elmander, swivelled inside the area and thumped a powerful effort past Mark Schwarzer, but Megson would like the player to add new dimensions to his game.

"Ivan would probably be as good a finisher as there is in the Premiership, but there are other things that he needs to add to his game to be a Bolton player," said Megson.

"We're not particularly good at going forward without using the forwards and we don't get too much down the sides so he has to link up the play a little bit more for us, as did Kevin Davies.

"There were a lot of really good things about our play but I just think the thing that was missing was when the ball went forward we didn't get hold of it and play from there to enable ourselves to get out.

"The way the game went, it would be a little bit much to say that we were that much on top that we're disappointed just to get a point.

"Craven Cottage has always been a difficult place for us to come and to get a result, so from that point of view it is pleasing. Everyone was disappointed with the outcome of the derby match last weekend and this gave us an opportunity to move on."