McCall has been thwarted in bids to sign Dean Furman and Andy Holdsworth this summer and, while he is still trying to bring in permanent signings, he admits that time is running out.
He told the Telegraph and Argus: "We are not sitting on our hands idle. I've said all along I needed two central midfielders - one definitely and probably two. But that's what the loan market is there for and I'm sure you'll see in the next couple of weeks a lot of teams using it.
"A couple of things that I was hoping would come off might not come off.
"It's frustrating. Believe you me, it's more frustrating from my point of view than it is for anybody else because I am doing work behind the scenes to make things happen.
"We had a lad from the Premier League, although it was not a household name and no-one would know him, we liked the look of but at the last minute a League One club came in."