Tiger Woods and Rory McIlroy will start as British Open favourites at Muirfield from July 18 but have question marks over them for the year's third major.
For Woods, the doubt is over a sore left elbow that has sidelined him since a poor showing at the US Open in mid June.
For McIlroy, the uncertainty is poor form since changing clubs.
Woods had a great start to the year, winning four tournaments, finishing fourth at the Masters and regaining the world No.1 spot from McIlroy headphone stand
It seemed odds-on he would finally add a 15th major to his career haul, the last coming at the 2008 US Open before his infamous sex scandal.
But all that changed at Merion as the inner elbow sprain he picked up in winning the Players Championship was worsened by blasting out of the thick rough in Philadelphia.
His worst showing in finishing a major championship was followed by a quick decision not to play again until the British Open four weeks away.
At the time, Woods said he was simply heeding medical advice.
"I listened to my docs. I'm not touching a club. We're treating it and eventually I'll start the strengthening process of it, then start hitting balls to get up to speed for the British," he said.
The 37-year-old, who has won the British Open three times (2000, 2005, 2006) has made no comments on the injury since then.
But with the rough at Muirfield set to be deep and punishing, anything short of full fitness could sink his hopes on a course where he shot his worst score as a pro - a 10-over-par 81 - the last time The Open was held there in 2002 hong kong companies registry
McIlroy has been similarly quiet in the build-up to the Open. He also struggled at Merion, where he tied for 41st, before missing the cut at last month's Irish Open.
The 24-year-old admitted he was still having problems with his new driver and would try to sort out the problems that have left him winless this year.
McIlroy was not tempted to tee off in the French or Scottish Opens, traditional warm-ups for the British.
"No, I am not going to add a tournament as I am going to take the next two weeks off," he said in Ireland.
Defending champion Ernie Els and four-time major winner Phil Mickelson entered the Scottish Open, but missed the cut, while Ryder Cup stars Luke Donald, Martin Kaymer, Ian Poulter and Graeme McDowell all opted to compete in France, where McDowell won for the third time this year custom embroidered patches
Justin Rose will seek to become the first player since Woods in 2000 to win back-to-back US and British Opens.
Muirfield will play 158 yards longer than in 2002 while new tees have been added at seven holes taking the overall distance from 7034 yards - when Els won 11 years ago - to 7192 yards.