Defending champion Casey pulls out of Houston Open

The world number six advised tournament officials on Thursday of an injury to his left shoulder and pain on the left side of his neck.

Casey had been due to tee off in the first round at 0800 local time with American Phil Mickelson and Australia's Adam Scott.

But rather than risk further injury by playing the $5.8m event the 32-year-old Englishman withdrew as a precaution before next week's U.S. Masters at Augusta.

"This injury is completely separate from the injury I had last year so I am not overly worried but my left shoulder is not comfortable while my first rib on the left side is not moving correctly, and the muscles around it have locked up so I am not able to get the club in a position where I can swing it properly and hit the golf ball," Casey told reporters.

"I tried to play on Wednesday and I am bitterly disappointed not to be going out and playing today but I have got to worry about the rest of the season.

"And after last year's experience of trying to play through an injury for about one or two weeks, it ended up costing me six months away from the game," Casey said.

"So the last thing I can try and afford is try and push it and cost myself anymore time. Hopefully, it is only a one week thing."

(Editing by Ed Osmond)