Manager Jan Molby is pleased with his start, and is set to offer the 24-year-old a contract, possibly until the end of the season.
This comes after the news that Richie Appleby is going to require surgery on a troublesome knee injury.
Molby confirmed: "Appleby is booked in to see a surgeon and he will probably require an operation. To be honest, I've switched off about when he will be available. It looks like it will be five or six weeks but we'll know more when we've spoken to the surgeon.
"It's good that Keates has come in because that means we've got more than adequate cover for Appleby. I've been delighted with him and I will be sitting down and trying to sort something out."