And Warburton is also missing the first match in Australia - against Western Force in Perth on Wednesday - as he continues his rehabilitation.
But Gatland is not overly concerned and hopes he will be in contention for Saturday's match with Queensland Reds in Brisbane.
"Sam has been doing some of his own training but he had to stay off his knee for five days before he is ready for full contact," said Gatland.
"Hopefully he will train with the other players not in this 23 over the next couple of days and put himself in contention for Saturday."
Meanwhile, Leigh Halfpenny, also of the Cardiff Blues, makes his first appearance of the tour in Perth, having sat out the match against the Barbarians, while Gethin Jenkins, who will return to the Blues next season, is hoping to take part on Saturday if he shows no reaction to a calf problem over the next 48 hours.
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