Eagle-eyed NYPD transit cops collared an “erratic” man on the subway who was carrying what appeared to be a blood-soaked machete, police sources said.

Officers on a station inspection on the C and E lines on 50th Street and 8th Avenue at around 11:30 a.m. Friday spotted a man on the southbound mezzanine platform acting in a disorderly manner, the sources said.

The man had the large blade — which looked like it was covered in red liquid — on his back, the sources said.

Justin Wojno, 43, was arrested without incident and charged with criminal possession of a weapon, the sources said.

No one was hurt, and the red substance turned out to be syrup, according to the source.

Wojno has a “handful” of prior arrests, including domestic violence assault and burglary dating back to 1999, the sources said.