The Eagles are two points clear of the drop-zone going into their final 10 games but the striker has been ruled out of Saturday's relegation six-pointer with Sunderland after picking up a hamstring injury in the draw with Swansea City earlier in March.
"Cham won't be available this week but we'll assess him in the middle of next week," Puls told reporters on Friday. "It's a hamstring and it's a pretty bad one, which is a blow for us because he's done so well.
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"We've played through Cham and played some really, really good football when he's played."
Though he has overseen an impressive turnaround in fortunes since taking over from Ian Holloway in November, the Welshman warns fans that they must be realistic about the size of the task still remaining.
Pulis remarked: "We've had such a great run that people forget this is the Premier League and this is going to be really tough. We've 10 games to go and we're playing teams who have been in it, seen it and done it before.
"I made one reference after the Southampton game - they brought on a midfield player [Victor Wanyama] who they spent £12 million on. That's what we're competing against every week and you have to keep your feet on the ground.
"The hard work and the effort that the lads have put in has been fantastic - [over] the next two months they have to do the same and, if anything, raise it a little bit more.
"People look at Sunderland's position and say it's a six-pointer but every game is an important game for this club."