Luke Donald has said that the European Tour should be "a bit worried" by the number of players turning to the PGA Tour.
Of the 24 golfers to play in this year's Ryder Cup, all except Paul Lawrie have expressed an interest in playing on the US Tour in 2013.
The world number three told The Telegraph: "If I was the European Tour I would be a bit worried, with a lot of the guys suggesting they are going to play their minimum [number of events] in Europe and concentrate mainly on the PGA Tour.
"I think that as a top player if you don't at least try it for a year or two you're going to have regrets.
"The European Tour just wants to cultivate the good players and continue obviously to be strong in the Ryder Cup. I do understand, though, if you're losing some of the top players it's going to be tougher to sign big sponsors to events."
Lack of sponsorship has resulted in four tournaments in Europe being cancelled this year, including the Madrid Masters and Czech Open.