Britain's world number three Paul Casey is out of this week's Barclays event in New Jersey, the first leg of the US Tour's FedEx Cup play-off series.

The 32-year-old is suffering from a rib muscle injury but hopes to return at the Deutsche Bank Championship in Boston next week.

Casey, a three-time winner this season, picked up the problem during a practice session before the Open last month.

"It has been a really frustrating few weeks," said Casey.

The Englishman came 47th in the Open at Turnberry but pulled out during the first round of the WGC-Bridgestone Invitational three weeks ago and missed the USPGA, the final major of the year which was won by YE Yang.

"I had hoped to be back out on Tour this week," added Casey. "However, I feel pretty lucky that it wasn't more serious and that the injury has responded to treatment so well.

"I am really hoping that it continues to improve and I will be teeing it up in Boston next Thursday."

Casey is still undergoing a course of intensive treatment, including having a cortisone injection to the intercostal muscle to assist the recovery of both a tear and a strain.

Earlier this month Casey lost his lead on the European "Race to Dubai" money list to German Martin Kaymer, and lies 18th in the FedEx Cup standings.

The end-of-season play-off series in the United States features four events, with the field whittled down after each according to the FedEX Cup points table.

Points accrued during the regular season count for the first three events.

Tiger Woods leads the standings with 125 players set to compete at The Barclays, 100 at the Deutsche Bank Championship (4-7 Sept), 70 at the BMW Championship (10-13 Sept) and 30 at the season-ending Tour Championship (24-27 Sept).