The Dutch centre-half has been absent for the past two games, defeats against Fulham and Manchester United, after being withdrawn at half-time in the victory over Southampton.
Vlaar injured his calf in that encounter and Lambert revealed he would assess the player this week at Bodymoor Heath in the run-up to the Potters clash on Saturday.
He said: "Ron is doing alright at the moment. Whether Stoke is too early for him, I will have to wait and see."
Meanwhile, Vlaar himself insisted he was desperate to return and said: "Like any other player, I do everything possible to remain at peak fitness but I felt my calf during the first half at St Mary's and it really stiffened up at half-time so there was no point in continuing.
"I was just delighted that the lads emerged from a very difficult game with all three points after a remarkable 3-2 win.
"Hopefully it won't be too long before I'm back because I remember how infuriating it was to be out of action last winter."
Forward Gabriel Agbonlahor will definitely miss the trip to the Britannia Stadium after picking up five bookings but Lambert will have midfielder Fabian Delph available again.
Lambert added: "Gabby being out is a blow. But on the plus side, Fabian is back. So that softens it a bit."