Howell has delayed his comeback yet again (Getty)

David Howell has delayed his golf comeback yet again and is now doubtful for next week's United States PGA championship as well.

The Ryder Cup star has not played since tearing an abdominal muscle at the US Open in June.

He was expecting to be partnering Colin Montgomerie in the first round of the Johnnie Walker Championship at Gleneagles on Thursday but did not come through Wednesday's pro-am as well as he thought he would.

"I just felt very weak towards the end," said the 30-year-old Swindon golfer, who had been in the form of his life prior to the injury setback.

"I found it a lot harder than I thought I would. I was a little more aware of it even on the first tee.

"It seemed harder than just hitting balls on the range and I'm obviously concerned about next week. A week is not a long time for the body to heal. It's touch and go.

"It's a case of withdrawing from here in the hope I'll be okay next week, but we'll just have to wait and see. The course is going to be set up like a US Open with thick rough and that's the hardest part.

"I've made slower progress than I hoped and it does not bode too well. I'm not overly-hopeful."

Howell expects to travel to America, but may wait until the NEC world championship in Ohio in a fortnight to make his competitive comeback.

Second on the European Order of Merit after losing play-offs for the British Masters and Irish Open and then coming fourth in the BMW Championship, Howell suddenly felt a rip in his left side warming up for his second round at Pinehurst.

It came completely out of the blue, but it left him wondering if he had done damage trying a heavy practice club belonging to Vijay Singh the previous day.

His place at Gleneagles was taken by Welshman Sion Bebb, who teed off in the star group of the day with not only Montgomerie, but also last year's Volvo PGA champion Scott Drummond.

Howell's main goal is to make sure he is fully fit for the start of the Ryder Cup campaign next month.

He is developing a reputation as an injury-prone golfer now.

Early in his career Howell was forced out of action when he damaged his ankle playing tennis and three years ago he was out jogging, tripped and broke his arm.

"I've had six or seven weeks off every year for the last four years, I think. I need to put a stop to that," declared Howell.

"It's been very frustrating to miss the tournaments I have, but the Ryder Cup points start soon and I am determined to make that team."