Onana pulled out of the Belgium squad that rounded off their Euro 2024 qualifying campaign last week after being forced off at half-time in Everton's win at Crystal Palace last time out.
Just a week earlier, Onana missed the Toffee's clash with Brighton & Hove Albion, with Dyche citing that fatigue on the muscle was affecting the player.
Ahead of Everton's clash with Manchester United on Sunday, Dyche told the media that Onana is not likely to be ready in time because of the issue.
Dyche revealed: "[Onana's] calf, I don't think he'll be right, it is still sore."
That means Everton's matchwinner from Selhurst Park, Idrissa Gueye is set to return to the starting lineup, but it will leave Everton short on numbers in midfield.
When Onana missed the fixture with Brighton, Dyche was unable to name a midfielder on his bench, showing how stretched the squad is when a couple of injuries creep in.
The sale of Alex Iwobi, and injuries to Andre Gomes and Dele Alli, without any replacements coming in mean Everton may be light on the substitutes bench again this weekend.
Dyche did provide updates regarding the fitness of Gomes and Alli though, stating both are back on the grass training, but not yet ready for a return to first-team action.
«Andre is back on the grass with us, which is good, he has had a very frustrating season so far with us but he is back on the grass, he needs a bit of time, he needs games obviously, but he's back around it.
»And then Dele, good to see him back on the grass, he's still tentative at the moment with the sports science side of things as regards not joining in with us,
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