The 31 year-old restored Atletico's lead barely 10 minutes after coming off the bench and also forced the foul which lead to Aderlan Santos being sent off for Valencia, before Yannick Carrasco sealed the win.
The Atletico favourite is expected to leave the club when his loan contract ends but Simeone paid tribute to him for his role against Valencia, who had drawn level in the first half through Denis Cheryshev after Antoine Griezmann had given Atletico the lead.
"Fernando responded as we needed him to, we know he is a unique player," Simeone said.
"We think about him every day, and today he had a huge impact when he came on the pitch.
"We won the game deservedly, playing really good football."
Torres admitted he did not expect to stay at the club beyond this season, he said: "The end of the season is getting closer with every day and the situation remains the same."
Atletico stay second in the Primera Division after recording a third straight league win, but Simeone admitted catching Barcelona, who are eight points clear at the top of the table, was not among his priorities.
"The real aim for us is to keep bettering ourselves," Torres said.
"It's what we try to do every year but it's not easy to do when we have so many new players. The average age of our team in this game was 24 years old and it's not easy when you have so many young lads. It's not easy to make them believe that the team must come ahead of everything else."
Valencia coach Gary Neville said his side had played well for certain spells in the game and rued individual mistakes costing his side again.
"Things didn't quite go for us tonight. I'm disappointed, probably the most disappointed I've been after a game," Torres said.
"We were playing against one of the best teams in Europe tonight by the way, and for 70 minutes we gave them one of the hardest games they've had. The second goal and the sending off changed the game, that was my assessment of it.
"We were in the game and in the last 20 it went away from us. I don't like repeat mistakes and it feels the same. I felt we could have got something out of the game."
Neville admitted he had not noticed that Santos had been sent off, explaining why he changed his mind twice about whether or not to bring on Alvaro Negredo, who eventually did enter the match.
"I didn't know Santos had been sent off initially, Alvaro was already coming on, then Alvaro told me Santos was coming off, sent off," Neville said.
"I then said to [Aymen] Abdennour, get changed you're coming on. The coaching staff called me back, said let's gamble, go with three at the back. We decided to gamble and we changed our mind again.
"We went back to the original decision because we decided with the coaching staff by drawing out how we could play, it definitely wasn't because of the fans. From my point of view, maybe sticking with the original decision might have been right."