Bellchambers has played one senior game for Essendon this season after being taken in the 2008 NAB AFL pre-season draft.
Hille will miss the rest of the season with a broken hand sustained against Adelaide on the weekend, while Laycock is suffering from a floating bone in the ankle.
Scans on Monday confirmed both Hille's injury and a broken fibula for luckless defender Courtenay Dempsey. Dustin Fletcher (groin) is also out of contention for the Bulldogs clash.
"Tom is quite a solidly-built young man, but he is a development player who is 18 years old, so he is going to get a chance to ruck against a really good ruckman in [Ben] Hudson," Knights said.
Midfielder Jason Johnson will definitely return to the senior team after a long-term calf injury, as will Mark McVeigh (knee) if he gets through training. Heath Hocking also looks likely to return having missed last weekend.
"We have got a few issues with injuries, but they are the cards you are dealt and the 22 that run out have really got to represent the club well on Friday night," Knights said.
"It's on a big stage against a good side so we have just got to wind them up to play good footy. We will potentially have to look at a few first-gamers, but we will take a look at them today and make a call."
