Saints are in the running via UEFA's Fair Play League, but Pochettino has confirmed that they will not accept the offer of a place.
The Argentine revealed though that the reason would not be fixture congestion - but because he believes all clubs who play in the competition should qualify by finishing high up their league.
"We would not accept it either if we were awarded that possibility," Pochettino said.
"We have spoken with the chairman and decided not to take that offer because I think in football what you are awarded in football needs to be earned on the pitch.
"We will only accept possibilities when we've earned them on the pitch and not just by fair play, but actually earning it with points and results."
Liverpool boss Brendan Rodgers says the Reds - who are also in the Fair Play running - would reject the chance to play in the competition for the same reason.