Yorkshire's dynamic young left-hander Michael Lumb is having a cartilage operation today and will be out for the rest of the season.

The 21-year-old South African-born batsman twisted his knee while fielding against Leicester-shire at Scarborough on Sunday and, in obvious pain, had to be helped off the field.

Lumb's absence comes as a serious blow to Yorkshire as they press to win the CricInfo Championship and the Chelten-ham and Gloucester Trophy.

They currently enjoy a 33- point lead at the top of the Division One table in the Championship, and next Wednesday meet Warwickshire at Headingley in the quarter-finals of the premier knockout competition.

Lumb, son of former Yorkshire opener Richard, has grabbed his opportunities this season and was well on the way to establishing himself as a permanent member of the side.

He scored his maiden first- class century in the last home game against Leicestershire and in four matches has made 218 runs at an average of 36.33.

"Michael was looking a very good batsman and it is unfortunate for himself and the team that he will be out of the remainder of the season," said Yorkshire captain David Byas.

Lumb's misfortune could pave the way for a return by Anthony McGrath, who has now recovered from the groin operation he underwent in late May.

Yorkshire were today due to face Baildon at Jenny Lane in a special match to mark the host club's 150th anniversary.