The shot-stopper limped off against Everton in August, with an initial prognosis of a 12-week absence predicted following surgery.
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"There have been absolutely no complications with Ben," Clarke told the club's official website. "It's just been a little bit slower than we thought because medicine and recovery from injuries is not an exact science.
"On the 12-week mark when we predicted he may be ready he was getting close and since then his progress has been good.
"Ben’s been back working outside for a couple of weeks now. He hasn’t joined the group for full training but he is back working with the goalkeeping group, which is just another step in the right direction for him.
"He’s progressing slowly but progressing well. He’s starting to see light at the end of the tunnel. He’s not too far away but I won’t tell you he’ll be ready in a week, two weeks, three weeks or four weeks."
Clarke has a number of other concerns ahead of the visit of Manchester City on Wednesday, with Nicolas Anelka unable to face his former side and Youssouf Mulumbu suspended.
Scott Sinclair, another injury absentee, is ready to return but is ineligible to face his parent club.