The 50-million-pound Spaniard scored his fifth goal in three games with a deflected shot after only 15 seconds of the second half, putting the English giants 2-0 up and coasting against the CONCACAF champions from Mexico.
"Fernando was, is, and always will be a very important player," Mata, who scored the game's opening goal in Japan, said.
"He's a great striker for us. We have a lot of confidence in him," the Spanish forward added, following the 3-1 victory at Yokohama's International Stadium.
Torres, who has struggled since his big-money move from Liverpool almost two years ago, came into the intercontinental tournament on the back of a brace in a 3-1 win against Sunderland on Saturday.
The world cup winner had not scored in the league since October 6 but had found the net twice in the 6-1 thrashing of FC Nordsjaelland in the Champions League prior to his double at the Stadium of Light.
His hot streak has coincided with a recent uptick in form under interim boss Rafael Benitez, with Chelsea having now scored 12 goals in their last three games.
Benitez said Torres was looking sharp and benefiting from increased confidence.
"If he has confidence it's easier for him and he'll have more chances to score," Benitez said after the win over Monterrey.
"We've been playing well and creating chances and he's around. It's good for him and good for us and I hope it will be the same in the future."
However Benitez, who lifted the Club World Cup with Inter Milan in 2010, suggested that Torres could still do more.
"As a team we did well. Fernando was part of the team and when you create chances he will score goals," he said.
"I think he was fine. He had one or two chances where I think he could have done better but I was pleased with his performance."
Torres, 28, was substituted after 79 minutes and replaced by Victor Moses.
Chelsea's third goal came courtesy of Monterrey defender Darvin Chavez who knocked the ball into his own net after Mata crossed following a pass from Torres. Monterrey scored a late goal in injury time through Aldo De Nigris.
Chelsea will play Copa Libertadores winners Corinthians in the final in Yokohama on Sunday.
Source: AFP
Source: AFP