The defender missed the 4-1 defeat to Manchester City after picking up a groin injury in the week leading up to the clash.
Instead, 22-year-old defender Ciaran Clark made his first appearance for almost two months and may retain his place against the Baggies on Saturday.
The Villans will be looking to respond against their near-neighbours after falling to their first Premier League defeat of the season at the Etihad Stadium.
But McLeish was focusing on Collins' injury and is hoping that the Welshman is back to 100 per cent by the weekend.
He said: "James just didn't make it against Manchester City. He had a groin injury. He hurt it during the week. I don't think he's too bad.
"We did a fitness test with him on Friday and he was clearly troubled by it. We don't think it's too bad though, but you never know. I don't want to count my chickens.
"James is one of these players who wants to train every day even when he has wee niggles. Sometimes we're going to have to save him from himself and make sure he's 100% fit and not every now and again 90%. That can take a sharpness away from your game."
Before Saturday, Clark had last played for Aston Villa in the Carling Cup against Hereford in August and is unlikely to play as many games as the 27 appearances he achieved last season.
But McLeish was full of praise for the Republic of Ireland international and says he is confident with the players waiting in the wings should Collins not make it.
He said: "The Man City match was an opportunity for Ciaran and I thought he acquitted himself well. There was no problem in terms of the goals and I don't think he was to blame at all. He is a good young prospect.
"We certainly need to try and keep all of our players fit, but when you have a player like James out, it's important that you have good back up.
"Ciaran is good back up and the good news was that Carlos (Cuellar) was on the bench as well. So he's not far away from fitness. He's a very, very, experienced defender."
Source: Team Talk