Injury scare forces out Casey

World No 3 a serious doubt for USPGA next week after tearing a chest muscle

Paul Casey's participation in next week's USPGA Championship was thrown into major doubt here last night when he was forced to pull out of the WGC-Bridgestone Invitational after just six holes of his first round. The Englishman has a pulled a muscle under his ribcage and now faces a difficult decision whether to risk his long-term fitness and tee it up at Hazeltine.

"I have to be careful as there's some big stuff coming up," explained Casey who is due to play seven events in the next nine weeks. "The guys in the physio truck have just told me it will take up to four weeks to be heal fully. I haven't got four weeks."

The 32-year-old revealed how he sustained the injury just before last month's Open. "I actually did it a week before the Open, hitting drivers with my coach, Peter Kostis," said Casey, who finished tied for 47th at Turnberry. "I didn't tell anyone, battled through the Open and have tried to rest it. I tweaked it in the rough on Monday. I've been in the trailer every day this week trying to get treatment on it, icing it, then hitting some golf balls when we're done. I was even par for six holes. But it just felt so bad."

It has been a miserable few months for Casey since he rose to world No 3 with his victory at the BMW PGA Championship at Wentworth. First he missed the cut at the US Open and then followed this setback, which could turn into something far more serious if he does not heed the advice of the medics. Casey is leading the "Race to Dubai" money list and with a pot somewhere in the region of $15m up for grabs at the November season-ender, the Englishman will be desperate to be 100 per cent.

Yet there was some richly positive news as well for European golf with the sudden return to brilliance of Padraig Harrington. After winning the last two majors of 2008, the Dubliner has struggled badly this year after making some well-publicised swing changes. Harrington believes he has turned a corner in time for his USPGA defence and his display yesterday spectacularly backed up that theory. A six-under 64 send him to the top of the leaderboard, two ahead of Thailand's Prayad Marksaeng and South Africa's Tim Clark.

This was the Harrington of old, perhaps not in the new truncated motion, but certainly in the way he confidently plotted his way around Firestone. The manic stare was back as was the peerless short-game. There was the occasional loose shot; most notably on his 15th hole (the sixth) when his approach from the middle of the fairway found the greenside bunker. But a putt from 10 feet saved Harrington's par there and then one from 25 feet on the next and then yet another of 12 feet on the penultimate hole hauled him clear.

The leading Briton is Ian Poulter, who shrugged off his missed cut at Turnberry with a 67. One further shot back on two-under lurks the overwhelming favourite Tiger Woods, despite yet another wayward day with his driver. Meanwhile, on level is Phil Mickelson, making his first appearance in six weeks following his wife's recent treatment for breast cancer.