"Alfie's got a syndesmosis [high ankle] injury, he'll see the specialist tomorrow so we'll know more from that. It's not the greatest but it's not an out-and-out disaster but that's his injury."
The hooker, who has starred in the back row for Wasps to move to eight tries in 12 senior games, could face a spell of up to eight weeks on the sidelines.
Blackett added: "It's hard to know because there's still question marks here in terms of will he need surgery. If he needs surgery he'll be a fraction longer than that, if he doesn't I think you're probably around the right point [six to eight weeks] but you're guessing game here. Until he sees a specialist which is due tomorrow then we'll know a lot more from tomorrow night, what's happening."