2...Nf6!? is the Nimzowitsch Variation. 3.e5! is the only attempt at refutation, e.g. F Rhine vs D Sprenkle, 1981. Doubtless Cardoso didn't want to walk into Gerusel's home preparation.

Although Nimzowitsch had introduced 2...Nf6 40 years before, the theory of this line was still in its infancy in 1957. What is today the main line, 3.e5 Nd5 4.Nc3 e6 5.Nxd5 exd5 6.d4 Nc6, was only introduced two years later in Gligoric vs Larsen, 1959. Nimzowitsch liked to play 4...Nxc3 5.dxc3 b6?? (other moves are playable), but that was later discovered to be refuted by 6.e6!!, Rellstab vs W Schoenmann, 1932; Petrosian vs N Grigoriev, 1945. Another known line at the time was 4...e6 5.Nxd5 exd5 6.d4 d6, which Keres had annihilated in the famous game Keres vs W Winter, 1935. But Keres had sacrificed many pawns in that game, and it's certainly understandable if Cardoso didn't want to go into that line unprepared.

3.Nc3 is sensible if one hasn't studied 3.e5. Black's most solid course is to transpose into main lines of the Sicilian. He can also avoid them with 3...d5 or 3...Nc6 4.d4 d5, as here. Houdini 3 says that White gets about a +0.4 advantage by grabbing the pawn with 5.exd5 Nxd5 6.dxc5 Nxc3 7.Qxd8+ Nxd8 8.bxc3 f6 9.Be3 e5 10.Nd2.

The line Cardoso played allows Black to equalize easily with 8...exd4 9.Nxd4 e5 10.Nxc6 Qxc6. Gerusel's 8...e5?! looks, and is, bad. White's best response is 9.Bd3! Qg4 10.h3! Qh5 (10...Qxg2?? 11.Rh2) 11.d5 with a large advantage. Cardoso's 9.dxc5 is harmless and allowed Black to equalize.