Pochettino rotated his squad for Spurs’ FA Cup match yesterday, but Townsend was not even handed a place on the substitutes’ bench.
The 24-year-old’s omission has added credence to the suggestions that he could be about to leave White Hart Lane.
And Pochettino said: "I can pick only 18. You need to put out another player when you pick some names. Always it's about my vision, my opinion, and what I see in the training sessions."
Townsend has not been seen in a Tottenham shirt since October, and he has only made seven appearances all season.
The wide man is yet to make a Premier League start in the 2015/16 campaign, with Pochettino clearly favouring other options in his squad.
Southampton, West Bromwich Albion and Newcastle United are all said to be interested in signing the England international in the coming weeks by the London Evening Standard, and his latest omission should offer them hope that a deal could be possible.
If Townsend does leave Spurs in January, he will do so having made 93 first team appearances for them, since progressing through their youth academy.