Madrid  - Real Madrid midfielder Ruben de la Red could be suffering from the heart condition myocarditis, according to sports daily AS on Tuesday.

Myocarditis, a serious heart problem, is inflammation of the myocardium, the muscular part of the heart. It may cause chest pain, rapid signs of heart failure, or sudden death.

De la Red, 23, dramatically collapsed during Real's October 30 cup match away to third division Union Irun. He was stretchered off and rusehd to a local hospital, where he remained for two days.

He has not played since then, and has undergone several tests, the results of which have not yet been released by the club.

If De la Red is suffering from myocarditis, it is not clear if he will be able to continue as a professional footballer.

AS reports that he will undergo tests next week in Barcelona, at the clinic of a famous cardiologist - and that he might undergo further tests in London.

The sports daily quotes him as saying that "I am convinced that I will play football again."

De la Red was part of the Spain squad which won the 2008 European Championship, after a successful season on loan from Real to Getafe.

Spanish football has been very sensitive about possible heart problems for players, after Spain and Sevilla left-back Antonio Puerta died four days after suffering a massive heart attack during the August 2007 clash between Sevilla and Getafe.