Forty-one-year-old Emergency Service Unit Detective James Griffin noticed a man jump into the trackbed of the southbound N train at the Midtown station about 7 a.m., according to authorities. Griffin then jumped down and struggled to pull the man up off the tracks, police said.
The man, 29-year-old Richard Wilcox, fought back, causing Griffin, an 18-year veteran of the force, to hit his head on one of the subway rails, knocking him unconscious, police said.
Other responding officers were able to subdue Wilcox, and Griffin was rushed to Bellevue Hospital, where he regained consciousness and is in stable condition, police said.
He appeared to be in good spirits and received a visit from Police Commissioner Raymond Kelly.
The MTA said subway service on the line was suspended in both directions for about 30 minutes between 57th Street and 34th Street.
Wilcox was taken to Bellevue Hospital, too, police said.
He faces charges including reckless endangerment, resisting arrest and criminal trespass.