The Zaitsev Variation (also called the Flohr–Zaitsev Variation) was advocated by Igor Zaitsev, who was one of Karpov's trainers for many years. A Karpov favourite, the Zaitsev remains one of the most important variations of the Ruy Lopez. With 9...Bb7 Black prepares to put more pressure on e4 after 10.d4 Re8 11.Nbd2 Bf8, when play can become very sharp and tactical. One drawback of this line if Black is playing for a win is that White can force Black to choose a different defence or allow a draw by repetition of position with 11.Ng5 Rf8 12.Nf3. Today the theory in the Zaitsev variations extends beyond the middlegame, and it is rarely seen at the top levels because of the need to remember a lot of theory.