Late in Atletico Madrid's match against Deportivo la Coruna, Torres challenged an opposing player for a ball in the air, which resulted in the two colliding heads.
Torres was hit by the head of Deportivo midfielder Alex Bergantinos.
Players from both teams and fans at Riazor Stadium watched with apprehension as doctors worked on Torres, some putting their hands to their heads and others covering their faces.
Atletico Madrid striker Fernando Torres has been admitted to hospital after being knocked unconscious.
Atletico then provided a further update, writing: "Thanks for the messages of support for Torres".
Players from both sides rushed to the striker's aid, as did referee Carlos Clos, before Torres was eventually stretchered off the pitch with a number of his team-mates in tears. "It's just been a scare. He will spend the night under observation", Atletico tweeted. "I hope to be back very soon".
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Torres was taken to the hospital, where he was treated for the injury.
Atletico responded after half-time and equalised in stunning fashion 22 minutes from time when Antoine Griezmann thrashed home a shot from fully 30 yards.
He'd only been on the field for 20 minutes, substituting Kevin Gameiro.
Simeone said: "We still don't have any official information but he's conscious". "We are only anxious about Fernando's health at the moment".
Everton talisman Romelu Lukaku also wrote: "A speedy recovery to my former teammate", with a prayer emoji. The draw kept Deportivo one point above the relegation zone, and dropped Atletico 11 points behind leader Barcelona, which routed Sporting Gijon 6-1 on Wednesday.