Chess Openings Lab
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Sicilian Defense: O'Kelly Variation, Yerevan System

The Yerevan System of the O'Kelly is 3.Nc3, developing and keeping an Open Sicilian with d4 as an option. Black can choose a Kan-type setup with ...e6 and ...b5, while White aims for d4, Nxd4 and an English Attack plan with f3 and Be3.

Moves
1.e4 c5 2.Nf3 a6 3.Nc3
ECO
B28
Engine
+0.20 · level (Stockfish 17.1, depth 20)
Played
729 games in our lichess sample
White scores
50.7%

Key ideas for both sides

White

  • Play d4 and take back with the knight; with Nc3 already out, f3 and Be3 come quickly in all three engine lines.
  • After ...b5 and ...Bb7, f3 blunts the long diagonal and protects e4, letting White castle long behind it.
  • Against ...d6 and ...e5, retreat the knight to b3 and play for the d5 square with the c3 knight.

Black

  • ...e6 followed by ...b5 and ...Bb7 puts pressure on e4 and uses the a6 move well.
  • Play ...b5 early, before White's f3 and Be3, so the pawn can hit the c3 knight with ...b4.
  • The 3...d6 move leads to a classical Open Sicilian after d4, where ...Nf6 and ...e5 are the main resources.

Plans and pawn structure

Since White has committed the queen's knight to c3, an Open Sicilian with d4 is the natural follow-up. Black's ...a6 then works with ...e6 and ...b5 to put the bishop on b7 against e4. White answers with f3, Be3, Qd2 and long castling, then pushes g4 and h4 against Black's king. Black's counterplay comes from ...b4 hitting the c3 knight and ...d5 breaking in the center.

Where the engine's main line heads: Open Sicilian: White traded the d-pawn for Black's c-pawn. An Open Sicilian: White traded the d-pawn for Black's c-pawn. White has a lead in development and the d-file, Black has the half-open c-file and two central pawns.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position +0.20: level. Its three top choices for Black:

  1. +0.20 3...e6 4.d4 cxd4 5.Nxd4 b5 6.f3
  2. +0.22 3...b5 4.d4 cxd4 5.Nxd4 e6 6.f3
  3. +0.36 3...d6 4.d4 cxd4 5.Nxd4 Nf6 6.f3

Pawns, from White's side.

How it scores on lichess

729 rated lichess games reached this position; White scored 50.7%.

under 120042.7%
1200–159948.1%
1600–199952.2%
2000 and up55.8%

Light: White wins. Grey: draws. Dark: Black wins. About the sample.

How to play against it

As Black, decide early between ...e6 with ...b5 and ...d6 with ...e5. Get ...b5 in before White's pieces are set up, so ...b4 is a real threat. Avoid slow moves that let White build f3, Be3 and Qd2 without any pressure on e4.

Questions

What are the moves of the Sicilian Defense: O'Kelly Variation, Yerevan System?

The Sicilian Defense: O'Kelly Variation, Yerevan System starts 1.e4 c5 2.Nf3 a6 3.Nc3. Its ECO code is B28.

Is the Sicilian Defense: O'Kelly Variation, Yerevan System good for White?

Stockfish 17.1 rates the position +0.20 at depth 20, which is level. In 729 lichess games from our sample, White scored 50.7%. Suits White players who enjoy sharp Open Sicilians with opposite castling, and Black players who like fast queenside expansion.

What is the main idea of the Sicilian Defense: O'Kelly Variation, Yerevan System?

White develops with Nc3 and keeps d4 for the next move. After d4, Black's ...a6 supports a quick ...b5 and ...Bb7, while White builds an attacking setup with f3, Be3 and Qd2.

What should Black play next?

The engine's first choice is e6, with b5 and d6 close behind. 3...e6 keeps ...b5 and ...Bb7 ready and waits for d4 before revealing more.

Updated October 2026. Sources and method.