Benítez, 32, was recruited to provide competition and cover for FA Cup-winning goalkeeper Dean Henderson to help handle greater fixture congestion in their maiden European campaign.
However, despite Benítez's Champions League experience, Eagles boss Glasner opted to start Henderson in both legs of last month's Conference League qualifier against Fredrikstad.
Meanwhile, Canvot, signed from Toulouse on deadline day, will cover at centre-back for one of Chris Richards or Marc Guehi.
"Everyone who was available on Saturday still is. Nobody is returning for the Millwall game, but it looks positive that Adam Wharton and Eddie Nketiah will return for the West Ham game.
"There will be a few changes. I can confirm Walter Benitez and Jaydee Canvot will get their Crystal Palace debuts.
"Some players need to rest after international duty and playing many games, but not too many. There’s still a day and a half to go, so let’s see — but I have already decided to start them.
"At the moment, there is no plan for the rest of the season regarding the goalkeeper. Dean is our clear number one and he deserves it. He is doing an excellent job.
"Walter is great in training and has a lot of experience. He plays for Argentina, played with PSV, many international games.
"It's good to have him in the building and that's why we completely trust him. It's the same with Dean with England, even if he didn’t play, he was always on the road.
"Sometimes it’s mentally exhausting, then if we think it's good to give him a break and then we will play Walter. He is a great goalkeeper and a fantastic guy. We will decide it week by week."
**More to follow.**