Law missed the month of March with a knee injury, while Knight-Percival sat out last Sunday's trip to Scunthorpe United after picking up a nasty cut in training on the eve of the game.
Ahead of this weekend's Sky Bet League One fixture with the Saddlers at the Northern Commercials Stadium, McCall has confirmed that Law is now back in full training with the rest of the first team squad.
Knight-Percival is due to have his stitches out ahead of the Walsall match and he could even play with some form of head protection on if needed.
McCall said: "Lawsy is now totally pain free and he has trained today (Thursday).
"He has no problems with the injury now so he can come back into consideration.
"Nat is the same, he also trained with us this morning.
"He hasn't actually done any heading yet but he is due to have his stitches out. He had a head guard on and he is more than confident that he can play his part.
"We will have a look at him tomorrow (Friday) but I don't see any doubt really."
On top of the return from injury for Knight-Percival and Law, McCall is also expected to have Josh Cullen and Colin Doyle available to him as well on Saturday after the pair came back unscathed from recent international duty.
McCall added: "Josh Cullen will be back for us after last weekend, while Doyley is also back fine after returning to Ireland on Tuesday for their friendly with Iceland.
"I believe at one stage there was the possibility of him getting on for a cap. With Ireland losing the match though, I think their manager wanted to get some strikers on the pitch to try and change the game.
"Their management staff have been really pleased with his work with them.
"With those two back safely, it only really leaves the long-term injured like Alex Gilliead, Matthew Kilgallon and Reece Webb-Foster still out. We will certainly have more options available to us this weekend."