Vlaar has been missing with a calf injury and, during his absence, Lambertâ€™s team have failed to win in five.
The manager said: "Weâ€™ve got one fit centre-half (Nathan Baker) at the moment.
"We will see how Ron is and then decide if we have to adjust. Heâ€™s doing a lot better but sometimes itâ€™s needs-must."
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