World number three Paul Casey will decide today whether or not he will take part in this week's US PGA Championship.

A strained intercostal muscle, in his ribs, caused Casey to withdraw from last week's WGC-Bridgestone Invitational in Akron, Ohio, having played just six holes of his first round at Firestone Country Club on Thursday.

The Englishman, who remained at number three in the latest Official Golf World Rankings despite his withdrawal, wrote on his website that the problem "leaves me uncertain for this week".

Casey remained in Akron for the duration of the tournament to receive treatment from PGA Tour physiotherapists before heading to Hazeltine National in Minnesota on Monday.

He wrote: "I will ...not hit any balls until Tuesday and then make my decision.

"The injury actually came about in the lead-up to the Open when I was hitting drivers the week before.

"I've been able to rest it the past few weeks but tweaked it (last) Monday playing out of the rough.

"It's a frustrating injury to receive as the only real cure is rest. I will hope this improves so I can initially participate in the PGA Championship.

"We then have an important run of events for the FedEx Cup and also the Race To Dubai, so I will hope that any lay-off is as short as possible."