World number one Rafael Nadal admitted shock defeats to David Ferrer and Nicolas Almagro in recent weeks have shaken his confidence as he looks to defend his Madrid Masters title this week.

The 13-time Grand Slam champion has appeared almost unbeatable once he hits the red clay of Europe in recent years, but comes into Madrid having lost at the Monte Carlo Masters for only the third time in his career and for the first time at the Barcelona Open since 2003.

''Losing always creates doubts, anyone who tells you the opposite is lying," he said on Sunday.

"There is no benefit in losing. The easiest thing is to keep winning because everything comes naturally without thinking.

"When you lose you think more about where to move on the court, where to hit the ball, but that is what has happened and as I have said various times you cannot win in Monte Carlo or Barcelona 12 times.

"To lose twice in the quarterfinals is normal. Perhaps what has been abnormal is what has happened in recent years."