The 23-year-old collapsed for no apparent reason in Thursday's game two minutes before the quarter-hour mark, and was shortly stretched off.

The Spanish player was laying still on the pitch, barely moving on the stretcher and regained full consciousness in the dressing room.

He was hospitalized afterwards, and it turned out that he fainted as a result of extreme exhaustion.

The midfielder got back to normal in no time and flew to the Spanish capital on Friday, but still has to undergo further examinations.

Team coach Bernd Schuster seemed upbeat about Ruben's current health condition.

"I think Ruben is fine, but the doctor will make a more detailed analysis," the tactician told Real Madrid's website.

"We were scared at first because these things don't happen every day. Nevertheless, we soon found out it wasn't serious and grew calmer. We hope he makes a quick recovery."

Lackluster Performance

Concerning the game, the German coach said he's unsatisfied with his side's display on Thursday, saying the rearguard was a major weakness.

"I think the worst thing about the game was they way we defended. We were soft in defense, which benefited our opponent; this sort of team can be very dangerous in counterattacks," he said.

"We shouldn't despair because we still have to play the second leg at the Bernabeu. I think the fact that we knew this all along made the team relax too much."

Watch De la Red's collapse