It happened on the 1 platform at the 231st Street station in the Kingsbridge section around 7:30 a.m.
The 45-year-old man was standing on the southbound platform when he was pushed from behind.
He landed on the tracks but was not hit by a train.
He suffered a leg injury and was taken to North Central Bronx Hospital.
The attacker fled the scene.
So far, no arrests have been made.
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