The Belgian was forced off at half time during the 1-1 draw with Norwich City on Sunday, but despite the injury to the big-money summer signing from Aston Villa, McAllister is trying to remain positive when it comes to the club's strikers.
Danny Ings scored within three minutes of replacing Benteke at the weekend, while Daniel Sturridge made his first appearance of the season.
The Scot said of the 'refreshing' striker: "If anyone deserved a goal, it's Danny Ings. He's worked so hard on the training ground every day.
"Danny Ings has worked his socks off every day here. It's not a fluke. The return of Daniel Sturridge was also a positive from the weekend."
He also offered an update on the welfare of Jordan Henderson, saying the minor surgery he had on his broken foot went well, but there has been no precise timescale put on his return just yet.
McAllister also confirmed there will be changes from the XI that faced Norwich in midweek, but has said the squad is strong enough to cope, and has spoken of the importance of the competition from his own playing days at Anfield.
"It will still be a very strong side. Obviously when there's the League cup, Europa league, we've got to utilise squad but we want momentum," he added.
"Winning it was the start for us in 2001.You gather momentum, get belief. It led to really good season. We'll give it respect it deserves.
"We have done the prep on Carlisle. They will come here and be expansive. They did very well at QPR."
The former midfielder also commented on the pressure that Liverpool players face. After what looked to be a promising start to the season in their opening three games, that momentum has been stopped in its tracks by a five-match winless run in all competitions.
"Players have to thrive under the pressure here. You have to cope with those demands," said McAllister.
"It's up to the players to get the fans going, not for the fans to get the players going."
One man likely to be in contention to start on Wednesday night is promising home-grown midfielder Jordan Rossiter, who seems to be the player representing the bond between local supporters and the first team, and McAllister - who played a similar role to the teenager during his playing days - is a big fan of what the 18-year-old has to offer.
"I'm a big fan. It's important the fans have a local lad. He's tenacious, he wants to listen and learn. He wants to work on his movement, passing. He's a player all the coaching staff are happy with.
"I see it as a big boost for the academy."