"About what happened four years ago, it's a different match, we have different players, it will be a completely different match," Alonso said.
Uruguay knocked Portugal out of the World Cup in Russia with a 2-1 win, and face the same opponents in Qatar on Monday in their second Group H game.
"Portugal have a very good squad, they have excellent players, they have a wonderful coach with wide experience," added Alonso.
"That makes them a dangerous team. On the other hand, we also have our own weapons. We will try to win, we will bring our A game."
The South Americans drew their first game 0-0 against South Korea in a subdued performance, while Cristiano Ronaldo's Portugal beat Ghana 3-2.
"We analysed the game, we know it wasn't good enough, we weren't pressing enough ... We need to change our play. We were a bit slow," said Uruguay midfielder Rodrigo Bentancur.
"We know it is a crucial game tomorrow. We know that we need to win and that is what we will try to do. We will break our backs as we always do."
Betancur said football had moved on since the 2018 match.
"It will be a different game. It's been four years since that game and football has evolved. Now we play with more intensity and players are in a better physical condition," he said.
"They (Portugal) play very well with the ball, they play the spaces, they beat the back line of the defence, but we've been working on that and we will try to use our own weapons so that we cannot be defeated."
