The manager said he was delighted to give Vorm a chance, lauding his commitment to the club despite featuring in only five league games since the start of last season.
"He (Vorm) is professional. Players like him fight and show great quality and that's my problem ... It's difficult to say: 'We are playing you and not you'," he told a news conference on Friday.
"He complains with his performances in the training session. That's his way to complain. To show me he deserves to play. That is the way to complain to the manager and not knock on the door."
Spurs reached the Champions League last 16 with a stunning win over Real Madrid on Wednesday but the manager insisted they must maintain their high level of performances in the domestic league, where they trail leaders Manchester City by eight points.
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"I think we must be focused. We must work hard to try to get another good result on Sunday," Pochettino added.
"It will be tough always, it's difficult to play Wednesday because the effort was massive. But we must be ready – Crystal Palace have very good team."
Spurs defender Toby Alderweireld will miss the match after straining his hamstring against Real, while midfielder Victor Wanyama continues to recover from his knee problem.
Bottom-placed Palace have collected all of their four points this season in last three matches after losing the first seven without scoring a single goal.
(Reporting by Hardik Vyas in Bengaluru; Editing by Alison Williams)
