Karpov tried 9...Nd7 several times in the 1990 World Championship match, but Kasparov achieved a significant advantage against it in the 18th game. It is solid but slightly passive. Confusingly 9...Nd7 is also called the Chigorin Variation so there are two variations of the Ruy Lopez with that name, but 9...Na5 is the move more commonly associated with Chigorin. This defence is also known as the Keres Variation, after Paul Keres.