The former Bolton player joined the club in the close season after leaving Preston, but after picking up the injury in Saturday's friendly defeat to Hearts, the defender will be made to wait for his first league start.
Mark Bradley looks set to deputise with fellow right-back Dale Tongue currently suffering with an Achilles problem.
Evans told the club's official website: "Nicky will be out for around a month.
"He has a 50% tear in one of his hamstrings so that is not good news.
"We still have options at the back. I didn't think Mark Bradley looked out of place and that is credit to him."
- Mark Bradley