World number three Maria Sharapova slumped to a surprise 6-4, 6-4 defeat against German Angelique Kerber in the Paris Open Tennis quarter-finals.The top-seeded Russian broke first in both sets but failed to take her chances and was eventually eliminated when she hit a forehand out on match point.Sharapova, who reached the final of the Australian Open last month, said that she did not take Kerber lightly. Kerber was delighted after beating a top-five player for the first time in her career.