The odds on Paul Casey winning the European Order of Merit have shortened today after David Howell rated his chances of teeing off in the Volvo Masters at Valderrama tomorrow as only "50-50 at best".

Howell pulled out of today's Pro-am because of a shoulder injury and is hoping that the extra rest will allow him four good rounds in the competition proper.

"I've got a voice on each shoulder - one saying go home and stop being ridiculous, the other saying I might regret that decision," said the Ryder Cup player.

"Golf and my body don't particularly go together, which is a bit of a bummer. I know I should have been England football captain.

"I'm very fearful of playing and then having six to eight weeks off. It's a big decision and I'm struggling to make it."

If he plays, Howell will tee-off with fourth placed Swede Robert Karlsson - 10 minutes ahead of the second placed Padraig Harrington and Casey showdown - because the order of play reflects the money list.

If Harrington wins the tournament he will take the money list as well and even a top-three finish would leave him with a good shout. Karlsson and Howell need at least a top-two finish to have a chance finishing top of the pile.

However, Casey believes a fit Howell would have wrapped up first place by now.

"I really feel great sympathy for David. He's one of my best mates and I truly believe he should be leading this," he said today.

"I think he would be a long way ahead if we had seen a healthy David Howell all year. When you beat somebody who's injured it's kind of a hollow victory."

He is not going to dwell on Howell's misfortune, however, and is focused on his own game. "I've really got to worry about myself. It's not motor racing where you can block another guy.

"My goal is to put myself into contention on Sunday. There's nothing I can do in terms of how the other guys play.

"If I win the event that takes care of it."