Following a goalless draw in the first leg, Santos grabbed two early goals to almost cause an upset. Nevertheless, Monterrey overturned the 2-0 deficit in a late grandstand finish to claim the title.
De Nigris, who grabbed two goals during the final, has praised his team-mates and says it was an unbelievable finish to the match.
''When we were behind 2-0 against a great team like Santos, you can't imagine rallying like this. Now we are a team that has proven ourselves and made some history,'' he told reporters after the game.
Monterrey coach Victor Vucetich was also pleased with his side's success and commended their determination after going behind to emerge victorious.
He said: ''This is an extraordinary achievement for the boys. It's a credit to them and a great satisfaction for this group that worked so hard."