The injured Al Ahli striker was conspicuously missing in coach Avram Grant's 23-man list announced by the Ghana Football Association on Thursday.
The Black Stars are set to face the Pharaohs at the Borg El Arab Stadium in Alexandria in the second group game of the Africa zone qualifiers.
“It is very sad, I think is going to be a big blow for us,” Johnson told Kasapa FM.
“Gyan has been our reliable goal scorer, and we know he can get goals on a good day.
“It is not good news for us. This is a crucial game for us, and we need a player like Asamoah Gyan.
“It is very unfortunate we will be missing his services, but let’s hope for the best.”
Ghana are two points behind Egypt on the standings after matchday one.
The Black Stars were held to a scoreless stalemate by Uganda in Tamale, whereas Egypt came from behind to claim a 2-1 away victory over Congo in Brazzaville.
Gyan is Ghana's all-time top scorer with 48 goals in 96 appearances.
Having seemingly hit a good form after a loan move to Ahli from Chinese outfit Shanghai SIPG, the frontman suffered an injury in club training on Tuesday, ruling him out of the Egypt showdown.