After 1… Rb6 2.Nxa4 black’s important piece for the attack goes off the board. But
1…Nf4 2.Qc2
(2.Bxf4 Rxc3 3.Qxc3 Nxc3+ 4.bxc3 Rb6+ white has insufficient compensation for the Q)
2…Rb6 3.b3 Nxc3+ 4.Bxc3 Rbc6 5.Qd2 Bf5+ 6.Ka1 Rxc3 7.Qxf4 g6 8.Rg2 Qa5 9.Rb2 Rc2 10.Bd3
(10.Rxc2 Rxc2 11.Qb8+ Bc8 black has the attack )
10…Bxd3 11.Rxd3 Qe1+ 12.Rb1 Qe2 is a clear win for black.
Looks like 1….. Nf4 fits the bill tempting to remove one important support of c3 ,white Q having no good place to run away.
1 rb6 with dual threat on king & queen.
knight is overworked.
After 1… Rb6 2.Nxa4 black’s important piece for the attack goes off the board. But
1…Nf4 2.Qc2
(2.Bxf4 Rxc3 3.Qxc3 Nxc3+ 4.bxc3 Rb6+ white has insufficient compensation for the Q)
2…Rb6 3.b3 Nxc3+ 4.Bxc3 Rbc6 5.Qd2 Bf5+ 6.Ka1 Rxc3 7.Qxf4 g6 8.Rg2 Qa5 9.Rb2 Rc2 10.Bd3
(10.Rxc2 Rxc2 11.Qb8+ Bc8 black has the attack )
10…Bxd3 11.Rxd3 Qe1+ 12.Rb1 Qe2 is a clear win for black.