Pochettino, whose Saints side aim to heap more misery on the Spaniard at St Mary's tomorrow, said: "I have played against Torres many times and he scored some goals against me.
"I remember him being a quality player, full of strength and a player who knew which spaces to run into to create chances. Sometimes it happens where a player is comfortable and feels happy at a certain club as he was at Atletico and at Liverpool.
"But when you leave that club and join a new team maybe you do not feel as comfortable and as happy and that can affect your performances.
"I do not know if Torres will leave Chelsea but what is clear is there is no doubting his quality."