Slack bowling by Yorkshire in the morning put the Championship leaders on the back foot in their vital match against title-holders Sussex, who closed the first day at Hove strongly placed on 386 for five off 107 overs.

Anthony McGrath took over the captaincy in place of the injured Darren Gough and his first big disappointment was to lose the toss on a good batting pitch which is certain to assist the spinners as the game progresses.

Then, in the evening session, with the score on 331 for five, McGrath collapsed at mid-off just as Matthew Hoggard was delivering the final ball of an over.

It was some time before other fielders realised what had happened and McGrath was on the ground for several minutes before being led off by physiotherapist Scott McAllister, Michael Vaughan then leading the side.

McGrath was checked over by a doctor and it was felt that he had probably been overcome by the heat on an unusually warm day. McAllister said the player was being given a lot of fluids and that he should be fit to resume today.

Adil Rashid and debutant leg-spinner, Imran Tahir were both called into the action earlier than Yorkshire would have liked and although Tahir bowled tidily, it was Rashid who picked up a couple of wickets, including Michael Yardy, who led the Sussex assault with an unblemished 119 off 218 balls with 17 boundaries.

Ajmal Shahzad, coming in for Gough, shared the new ball with Hoggard and gave Yorkshire early hope by dismissing Chris Nash lbw in his second over with the score on nine.

But Richard Montgomerie and Yardy quickly put Sussex in control against bowling which was too short and off line and the majority of the runs came from well-middled strokes square of the wicket.

By lunch the second-wicket pair had added 140, with both batsmen completing their half-centuries, and it was into the afternoon before Tim Bresnan ended the stand of 178 in 47 overs by bowling Montgomerie for 73 from 140 balls with eight fours.

Yardy moved resolutely on to his century but at 119 he played the increasingly confident Rashid off bat and pad and was caught one-handed by Andrew Gale sprawling forward at silly point, the left-hander having struck 17 fours off the 218 deliveries which he received.

Murray Goodwin had moved briskly to 47 when he edged a leg-break from Rashid and was snapped up at slip by Jacques Rudolph.

Chris Adams, who reneged on the Yorkshire captaincy soon after his appointment last November, took three consecutive fours through the on-side off Tahir but he reacted quite angrily when given out lbw for 46 to Hoggard, who had returned to bowl four overs of reverse swing with the old ball

* Yorkshire's Richard Pyrah, has had his contract extended until the end of 2009.