13.exd4
Apparently, Leitao didn't know his classics. In a later game against Mecking, Leitao (just like Karpov) decided to refuse the sacrifice with 13.Qb1.

17...Qxb3 18.Qxb3 cxb3 was a safe alternative, where Black just keeps his extra b-pawn.

Now Black's weakened kingside gives White counterchances.

Finally.

A questionable decision. Now Black's king becomes a strong piece instead of a vulnerable one, and eventually Lima managed to convert his extra pawn:

and Black won the game in move 47.

“Your body has to be in top condition. Your Chess deteriorates as your body does. You can’t separate body from mind”
Bobby Fischer

What move would you play here? The natural and obvious 14...Nc4? What candidate moves did you choose between? You probably also considered several rook moves. Fischer, however, opted for...