Yorkshire gained an unexpected first-innings lead of 118 against Hampshire at the Rose Bowl yesterday - but their day was marred by two dropped catches at a crucial stage and an injury worry to fast bowler Chris Silverwood.

After his impressive start to the season, Silverwood is in the frame for a place in England's one-day squad this summer, but he was forced to limp off for ice-pack treatment on an ankle injury.

His departure was seen by England selector Geoff Miller, who was closely monitoring yesterday's play. Silverwood has a history of foot and ankle problems and last year on the same ground a chipped ankle bone caused him to have an injection in order to get through the C & G Trophy final a couple of days later.

He had expected to have an operation soon afterwards, but a specialist advised that it was better for the injury to heal itself after a period of rest.

"Chris started to feel pain in his ankle while bowling and it will be some time before we know the full extent of the problem," said Geoff Cope, Yorkshire's director of cricket.

"It is a bit worrying in view of what has happened in the past but if things are not too serious he may bowl in the second innings."

Silverwood was not alone in being discomforted yesterday because Steven Kirby also had to leave the field for a while for back treatment just after a dynamic burst had brought him three wickets for two runs in 14 balls.

Kirby's blast helped reduce Hampshire to 107 for seven when they still required 37 to avoid the follow on, but four runs later Ryan Sidebottom failed to hold a low return catch from Shaun Udal and in the following over Darren Gough had Nick Pothas dropped at first slip by Matthew Wood.

The eighth-wicket pair eased Hampshire out of their crisis by adding 47 in nine overs before Udal was the first of two batsmen in consecutive overs from off-spinner Richard Dawson to be caught close in off bat and pad. Last man Alan Mullally was caught behind at 175 giving Yorkshire a first innings lead of 118.

Wood and Michael Vaughan put on 23 in eight overs to the close to leave Yorkshire 141 in front, but with bad weather forecast they would have felt far happier if Hampshire had been forced to follow on. Yorkshire never imagined when they staggered to 128 for seven on the first day that they would end up with 293 and two batting bonus points, but an immaculate century from Michael Lumb and a bruising 72 from Gough got them there.

Continuing their overnight stand of 46 for the eighth wicket they had extended it to a priceless 126 in 30 overs when Gough edged Simon Katich to the wicketkeeper for 72. Lumb remained calm throughout his innings and when he had run out of partners he was left with a flawless 115 from 242 deliveries.

Silverwood soon ripped out skipper John Crawley's off-stump with a ball of fierce pace, but he could only manage a total of nine overs before limping off.