Potter Variation

The Potter Variation meets the Classical 4...Bc5 by withdrawing the attacked knight to b3, where it is safe and hits the bishop at the same time. Unlike the retreat 5. Nf3, it gains a tempo instead of losing one. Black nearly always plays 5...Bb6, which keeps the bishop on the a7-g1 diagonal and leaves the other pieces free to develop. 5...Qe7 6. Nxc5 Qxc5 concedes the bishop pair. The check 5...Bb4+, usually followed by 6. c3 Be7, is the Romanishin Variation. The sacrifice 5...Bxf2+ is rare and scores poorly for Black. The engine rates the position as roughly balanced.

After 5...Bb6 the main move is 6. Nc3. White typically follows with Qe2, Be3 or Bg5 and O-O-O, which often produces opposite-side castling. A typical line is 6...d6 7. Qe2 Nge7 8. Be3 O-O 9. O-O-O f5, in which Black counters in the center and on the kingside. Black's other main options are 6...Nf6, 6...Qf6 and 6...Nge7. White can also play 6. a4, usually met by 6...a6, or the modern 6. Qe2. The line is named after William Norwood Potter, and Vassily Ivanchuk and Magnus Carlsen revived it in the 2000s.