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The veteran limped off at half-time in Friday's game with Wolves. It looks like he has a ruptured Achilles which could mean he could sit out for the rest of the campaign.
Kevin Blackwell said: "I haven't had time to really talk to our medical team yet but it looks like it could be a ruptured Achilles, and if it is Ugo will be out for the season."
If the outcome is that Ugo will miss the rest of the season, then it leaves Blackwell with a dilemma. With only two recognised centre-backs (Morgan, Kilgallon) he may have to dig into the January transfer window.