Pawn and Two: A stronger line for Black at move 16 was: (-1.01) (24 ply) 16...Be7 17.Nb1 Qxd2 18.Nxd2 Bb4 19.Nf3 Ba3.
However, Marshall's move was also in Black's favor: (-.48) (24 ply) 16...Rc6 17.Qe1.
After White's move 17.Rc2, Marshall should concentrate his heavy pieces on the c-file by first moving his Queen to c7 before moving his King Rook to c8: (-1.08) (21 ply) 17...Qc7 18.Rfc1 Rc8.
As Hoffer has explained, Marshall made a miscalculation when he played 17...Rfc8.
After 18.Nxd5, Marshall went ahead with his planned move 18...Qxd5, under the impression he would gain 3 pieces for his Queen. While it was too late to prevent a disadvantage, Marshall should have rechecked his calculations, as 18...Qxd2 was a much better move than 18...Qxd5.
After 18...Qxd2 19.Nxf6+ gxf6 20.Rxd2 Rc2 21.Rxc2 Rxc2 22.Bxb7 Rxa2, and Black can still put up a fight: (.67) (25 ply) 23.d5 Bg4.