-6 M Laird (Sco) St A, M Lafeber (Ned) K, R Gonzalez (Arg) C, T Bjorn (Den) C Selected others: -4 M Kaymer (Ger) St A -3 R Fisher (Eng) St A -2 L Westwood (Eng) K, E Els (SA) St A, G McDowell (NI) St A -1 R McIlroy (NI) St A, P Harrington (Ire) St Alevel F Molinari (Ita) St A, C Montgomerie (Sco) St A +1 E Molinari (Ita) St A +2 P Hanson (Swe) St A
St A - St Andrews C - Carnoustie K - Kingsbarns
Westwood played a key role in Europe's Ryder Cup triumph
Ryder Cup star Lee Westwood suffered a recurrence of a calf injury on day one of the Dunhill Links Championship but will continue playing in the event.
Westwood, who carded a two-under-par 70 at Kingsbarns to lie four off the lead, would usurp Tiger Woods as world number one with a top-two finish.
Scot Martin Laird is joint leader after carding a 66, also at Kingsbarns.
"I felt a twinge and I panicked a bit. I've had treatment and I'm going to play on," said Englishman Westwood.
"Playing two weeks in a row was probably too much in hindsight.
"I felt it coming off the seventh tee. It was a really steep downslope and it's really aching now like I'm doing too much too soon.
"I should have gone back to rehab. My main priority has to be to get myself and my golf in the best possible shape for the Masters next year.
"I made a mistake two months ago playing in the Bridgestone Invitational when it was not right. I should have rested after The Open at St Andrews."
The Ryder Cup, in which Europe were victorious over the United States with Westwood scoring two-and-a-half points out of a possible four, was the 37-year-old's first competitive golf since August.
He pulled out on the second day of the Bridgestone Invitational in Akron, where he also had an opportunity to dethrone Woods.
Because of the bizarre workings of the ranking system, Westwood would have been certain to dethrone Woods if he had withdrawn and then missed his defence of the Portugal Masters next week.
By playing on the task is harder, but Westwood commented on the eve of the tournament: "That's not the way I want to do it. I want to get to world number one by playing the way I have for the last two years and proving I'm the best."
Laird, who plays most of his golf in the United States, shares the lead with Dutchman Maarten Lafeber (Carnoustie), Argentine Ricardo Gonzalez and Denmark's Thomas Bjorn (both St Andrews), an assistant-captain for Europe at the Ryder Cup.
Martin Kaymer, who carded a 68 at Kingsbarns, is the highest-placed Ryder Cup player, while England's Ross Fisher carded a 69, also at Kingsbarns.
Nine of Europe's Ryder Cup players are in the field, plus captain Colin Montgomerie.
"I've five years left (on the main Tour). I'm exempt to 2015 and I have to make an extra effort and attain new standards," said Montgomerie, who is playing with brother Douglas in the pro-am event.
"I've really got to work at it on and off the course. I'd love to be able to come back and win again.
"I'm still very ambitious and the fact that I'm 400th-odd in the world actually made it stronger."
The Dunhill Links Championship features 168 professionals and the same number of amateurs playing in two man teams.
The tournament is played on rotation on three courses, Carnoustie, Kingsbarns and St Andrews, with the latter also hosting Sunday's final round.