In his second world championship match against Karpov, Moscow 1985, Kasparov scored all his three victories as White with this variation. So it is small wonder that this gave some impetus to the popularity of the line which is now known as the Kasparov Variation. One peculiarity of 4.Nf3 is that a lot of transpositions to other openings are still possible.
The Leningrad and the Kasparov Variations may be seen more rarely than 4.Qc2 or 4.e3, but Kasparov’s example shows that they can, nevertheless, be very successful.
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