The powerful back-row forward returned from a fractured forearm suffered in January to feature in the 51-14 victory over London Irish on Sunday.
There were fears the 25-year-old had swiftly fallen victim to yet another fitness setback after he experienced an issue on Wednesday.
And while Vunipola is indeed set to miss Saturday’s regular-season Premiership finale against Gloucester, Saracens’ director of rugby McCall claimed his star should be back for the team’s subsequent last-four showdown against Newcastle Falcons or Wasps.
“[The hamstring] hasn’t been pulled or anything, as far as I know,” McCall was quoted as saying by the BBC.
“There are two and a half weeks until the semi-final, so all things considered it’s probably best he doesn’t play this weekend.
“If anyone has a hamstring tightness on Wednesday, it wouldn’t be the most sensible thing to play him [on Saturday].
“Maybe having not played rugby for a long time, these kind of things can happen quite easily.”
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