Darren Lehmann and Anthony McGrath both got themselves out when centuries were theirs for the taking against Somerset at Taunton yesterday.

But the real bad news for Yorkshire was a serious knee injury to skipper David Byas which will almost certainly require surgery.

The captain had made only two runs when he jerked back to avoid a short ball from Peter Trego and it was immediately obvious he was in great pain from his right knee.

Byas rarely suffers an injury of any sort, but he could barely hobble off the field after first been attended to in the middle by physiotherapist Caryl Becker who later took him to hospital where a torn cartilage was diagnosed.

Becker said that Byas would have a scan on Monday and an operation could follow soon afterwards, but she was reluctant to rule him out for the remainder of the season.

His absence will be a severe blow for Yorkshire as they attempt to maintain their challenge for the County Championship.

Yorkshire were going well at 175 for three when Byas limped off, but they then suffered a middle-order collapse and it was thanks to a career-best 68 not out from Ian Fisher, well supported by Championship debutant Simon Guy, that they managed a final total of 327 to trail by only 32 on the first innings.

Lehmann led Yorkshire out when they came back to field and at close of play Somerset had scored 33 without loss to extend their lead to 65.

Although several Yorkshire batsmen played some fine shots they were left kicking themselves for getting out to some casual strokes against fairly ordinary bowling.

Simon Widdup went early on, carving Steffan Jones to Trego at third man, and after McGrath had survived a low chance to Mark Lathwell at gully he and Vic Craven batted confidently and well until Craven slapped left-arm spinner Ian Blackwell tamely to Trego at mid-wicket and departed for 42.

Lehmann was in a bustling mood and straight after lunch he drove Blackwell for six before taking a couple of boundaries off his next over as he raced towards his ninth half century of the season off 58 balls with seven fours and a six.

McGrath's first 50 of the summer quickly followed, but when Lehmann had moved to 56 - which gave him exactly 1,000 runs for the season - he lashed out at Trego and was bowled off stump, his third- wicket stand with McGrath being worth 91 in 23 overs.

Soon after Byas pulled up lame, McGrath also surrendered to a moment's carelessness by returning a long hop to Blackwell for 74.

Gary Fellows and Gavin Hamilton both fell to Graham Rose, but Guy gave a nimble performance, and with Fisher striking practically everything to the boundary, Yorkshire's fortunes were revived.

Fisher's first six scoring shots were all fours and soon after the sequence had been broken he swatted Keith Parsons for a six, 92 runs coming off 27 overs before Guy swept at Parsons and was lbw for a gallant 42.

By then, Fisher had equalled his best score of 51 against Surrey at the Oval last year and he continued to hit out freely, making his runs off 83 balls with 12 fours and a six.