Birthday boy Andy Murray crashed out of the Madrid Open in straight sets at the hands of world number five Juan Del Potro.

The Argentine was simply too good for Murray, who could have have thought of better ways to spend his 22nd birthday.

The newly-installed world number three's frailties on clay - despite showing recent signs of improvement - were exposed and despite saving three match points, he went down 7-6, 6-3.

The Scot will now have to hope that top seed and tournament favourite Rafael Nadal beats Novak Djokovic in Saturday's semi-final or he'll drop a place in the world rankings ahead of the French Open in Roland Garros later this month.

Murray had a chance to serve for the first set after banking an early break, courtesy of an inch-perfect backhand cross-court winner.

But the British number one faltered when it mattered, Del Potro breaking back to take the opener to a tie-break that he bullied his way to comfortably.

Del Potro broke again in the sixth game of the second set and then quickly closed out the match to reach his second Masters 1000 semi-final of a breakthrough season.

However, world number two Roger Federer now awaits in Saturday's semi-finals.

And while Del Potro had a late night - his game didn't finish until half past midnight - Federer had a relaxing evening after beating Andy Roddick 7-5, 6-7, 6-1 earlier in the day.

He has now won 18 of his 20 encounters with the American and he looked in ominous form - booming down 15 aces and winning over 70 per-cent of service points.