Bianchi, 26, a summer signing from Sassuolo, damaged knee ligaments in the midweek win at Reading and requires surgery, which is expected to rule him out for at least two months.
Redfearn has made no secret of his desire to bring in two more players, with a left-sided midfielder at the top of his list.
"(Bianchi's) going to be out for a while now with his knee. It's a medial ligament injury and he's going to need an operation on that," Redfearn said.
"We're looking at a couple of months so he's perhaps out for the season. It's disappointing because he's a really good kid who works hard and tries his best.
"He's been out of the picture and he came back in the other night, I thought he was doing okay. It's disappointing for him but he's only young so he'll be back."
On his ongoing recruitment process, Redfearn said: "Jokingly I always say 'get me a left winger or a striker', but I understand how it works. If we can get the right players in, I think it's still important that we do that.
"I've mentioned certain players and we know the areas we're targeting. It's not a secret. But it's about getting the right ones in. If you can't, you might as well persevere with the ones you've got."
Millwall midfielder Martyn Woolford remains a target for Redfearn, who added: "He's got Championship experience, he scores goals and he gives you physical presence on the left.
"He gives you that balance and he's the type of player we're looking for. But Alex Mowatt did well the other night and we're playing him in that position, not his natural position, but he's warming to it."