Evatt becomes the third key player to be sidelined for new boss Michael Appleton with both Matt Phillips and Gary Taylor-Fletcher already unavailable through injury.
Appleton saw his side record their third-straight draw following Isaiah Osbourne's last-minute equaliser against Watford on Saturday and admits he needs to strengthen the squad.
He told the Blackpool Gazette: "It's easy to come up with excuses but I've lost three key players now. But that will happen to every manager and I have to trust the players who come in.
"If I'd have known Evo's injury would be so bad, I'd probably have tried to get cover in before Thursday (the loan deadline), but we didn't.
"Obviously January can't come soon enough now. Between now and then we need to work hard to identify the right people to bring in."