The forward's toe injury at one point left him unable to put on a boot.
Lambert said: "He got a problem with his toe, he picked it up the other night, and it was just too painful for him to go on with.
"It's giving him so much discomfort he couldn't get his boot on the other day, so we'll wait and see."
Unsure when Vlaar will be ready to return, Lambert said: "I don't think it will be months, nothing like that.
"It all depends on how quick the injury comes on."
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