West Ham striker Dean Ashton has undergone a third ankle operation.

Ashton has not played since September after suffering more problems with the ankle he broke while training with England in August 2006.

Specialist Niek van Dijk, who has operated on Cristiano Ronaldo and Michael Ballack, removed some bone debris from the ankle joint. Hammers manager Gianfranco Zola said: "We don't know when Dean will be back but it went very well and he is much better than before."

Yesterday, Zola pledged his future to West Ham, despite reports that Chelsea players want the Italian and assistant Steve Clarke to move to Stamford Bridge this summer.

Zola and Clarke are focusing on their FA Cup clash against Middlesbrough, whose only wins this year have been in this competition.

Although Gareth Southgate's side are low on confidence, Zola is not expecting an easy fifth-round tie.

He said: "I saw them at Manchester City last week and they played well.

"They may be going through a bad run but Gareth Southgate is a good young manager. He will have his team very concentrated and very well prepared."