The England winger broke down during the pre-match warm-up.
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Saka was set to start in the front three but was replaced by Noni Madueke after being forced to pull out before kickoff.
Saka was due to captain Arsenal at Elland Road with club skipper Martin Odegaard named on the bench.
He had been warming up as normal before being spotted heading down the tunnel with a physio.
Arsenal face Leeds sitting top of the Premier League table by four points.