Slade, who has started all four of England’s Six Nations games so far this campaign, suffered the lower leg injury at training on Monday, and was unable to train on Tuesday.
England are optimistic that Slade will be available to face Ireland, but have still felt the need to call up Marchant, who has been in fine form for Quins.
Marchant has been part of Eddie Jones’s “shadow squad” – who have been on standby but not in camp – through the Six Nations.
Strict Covid-19 protocols have prevented Jones from changing his 28-man squad except when a player is injured.
If Slade is not fit to face Ireland, Ollie Lawrence – who was recalled to the bench last weekend – would be the likeliest starter.
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