Portugal won EURO 2016 and came to Russian Federation with high expectations after the surprise title in France two years ago, its first in a major tournament.
"It's not the time to talk about the future when it comes to the players and coach", he added.
"I am convinced that he has a lot to give in football", said Santos, whose own future is in doubt after elimination here.
The World Cup lost its headline acts on Saturday as the game's two biggest stars, Lionel Messi and Cristiano Ronaldo, readied to leave Russian Federation after their teams were eliminated in the round of 16.
Cavani struck in the seventh minute of Saturday's last-16 tie in Sochi to put Uruguay in control, but Portugal hit back after the interval when Pepe headed home Raphael Guerreiro's cross.
Uruguay will play France in their quarter-final on Friday.
"Cavani has to thank Suarez today, but his movement has always been brilliant, finishing not always great but, for the first, he improvises brilliantly", said Keown.
Uruguay's Edinson Cavani (L) heads to score his team's opening goal against Portugal during their 2018 World Cup round of 16 match in Sochi on Saturday.
"I think there is often a mistaken assumption that possession leads to scoring opportunities", Tabarez said. "The team didn't win because Uruguay scored twice". But he made a decision to give the ball to Cavani, who has scored three goals in Uruguay's last three matches, including two in the win over Portugal.
Cavani received the ball from Rodrigo Betancur and sprayed a wonderful 40-yard diagonal pass to Luis Suarez.
Going on to suggest that "no single player" can contain him for ninety minutes, Tabarez went as far to name-check even his most revered defender, Diego Godín, as being incapable of carrying out the task.