Vydra limped off before half-time in last night's 3-0 win against Newport County and is now a major doubt for the Hawthorns meeting with the Swans.
Head coach Steve Clarke said: "He was running back after Goran Popov had given the ball away in a dangerous position. He just felt his hamstring tighten up.
"Rather than risk him, we took him off as a precaution."
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