Ferrero has struggled with illness and injury this year

The Spaniard, 24, has struggled with illness and injury this year and nearly withdrew before the tournament.

Andreev, ranked 77th in the world, had never won a Grand Slam match before.

But the Russian dominated the match, completing his victory in just over two hours to set up a third-round match with France's Julien Benneteau.

After taking the first set in 51 minutes, the young Russian grabbed a crucial break in the second set in the sixth game to lead 4-2.

It's very difficult to defend a title when you are not 100% Juan Carlos Ferrero

In the next four games, Ferrero failed to win a single point as Andreev went 2-0 ahead in the third.

Ferrero broke back to 2-1 down but it was brief respite with Andreev regaining the initiative immediately to restore his advantage at 3-1.

The two players swapped breaks, but the Russian always had the advantage, and won on his second break point with an ace.

After the match, Ferrero admitted he was still plagued by injury troubles.

"It's very difficult to defend a title when you are not 100%. I don't feel too good physically," Ferrero said.

"I can't get to the ball, I arrive too late. My rib, I guess, was okay but then I felt some problems, some cramps in the abductor muscle.

"I couldn't move so well. It was very difficult to stay in the match while coping with two injuries."

The Spaniard had reached the semi-finals or better in each of his four previous appearances in Paris.

Ferrero's defeat was only the fourth time the defending men's champion at Roland Garros has lost in the second round since tennis turned professional in 1968.