Defending champions Inter Milan collapsed to a stunning 5-2 home defeat by Schalke 04 in their Champions League quarter-final first leg at the San Siro on Tuesday.

Inter seemed to have put behind their 3-0 drubbing by arch-rivals AC Milan in the Italian Serie A on Saturday as they raced to a 1-0 lead with only 25 seconds into the game.

Midfielder Dejan Stankovic volleyed his side into the lead with a stunning hit from the centre circle, but Joel Matip levelled, just as Edu did before half-time after Diego Milito restored Inter's lead.

It was all downhill for the Italian champions after the break as Raul netted for Schalke, Andrea Ranocchia scored an own goal and Cristian Chivu picked up his second red card in four days, before Edu notched again to round off a miserable night.

Inter coach Leonardo was left shellshocked by the result, saying he could not imagine what had gone wrong.

"It has been a terrible week," he said. "We started so well, it was impossible to even imagine it would end this way. Schalke had six or seven shots on goal, scoring with five of them."

Ralf Rangnick, Schalke coach, was ecstatic about the result which he did not dare to imagine.

"It is surely the best game of my career. Had someone told us before the match that we would beat Inter by three goals, we would have had him declared crazy," he said.