Lee Westwood expects to have to go through the pain barrier in his bid to end Colin Montgomerie's five-year reign as European number one this week.

Westwood is nursing a rib muscle injury as he prepares for the Volvo Masters starting at Montecastillo in Jerez tomorrow. "I did it playing against Tiger Woods in the World Matchplay two weeks ago," said the 25-year-old, who is £45,265 behind Montgomerie in the Order of Merit race with just one event to go.

"I was hoping that a few days' rest would do the trick. But then I had a company day at Walton Heath last Thursday, and my first swing felt like somebody had stabbed me in the side."

Perhaps unwisely, he continued to play all 18 holes, then a few more at The Belfry in Saturday's gales, and it was only yesterday that he had the injury examined. He was told he had torn a muscle.

Instead of a full practice round Westwood, wearing a support belt, opted for the driving range and putting green, but does intend playing in the eve-of-tournament pro-am today.

Westwood will be number one if he makes a successful defence of the Masters title. Even fourth place could be good enough, but only if Montgomerie finishes outside the top 44.

Third-placed Darren Clarke is not out of the running either - but for the Ulster-man, £143,210 behind Montgomerie, nothing less than victory will do.

Clarke, armed with new irons and a new driver this week, has not written off his chances but points to the fact that he has won only once this season - the Benson and Hedges International in May - whereas Montgomerie has won three times and Westwood four.

"Their mental attitudes are a lot stronger than mine at the moment," he admitted. "I am getting there, but a lot slower than I hoped.

"I've only gone backwards once on the Order of Merit since I turned pro, but it just takes some people longer than others. It's being Irish, I think. I have a different outlook on certain things and sometimes I get more frustrated than I should.

"They have taken their opportunities to win this year, and I haven't - hence the gap at the top."