Mets uber prospect Fernando Martinez is getting perilously close to wearing the dreaded “oft-injured” collar. The speedy, big-hitting outfielder is hurt again, having been sent back to New York from the Caribbean Series for tests on a sore elbow mandated by the Mets. The injury came just days after Martinez blasted a clutch, two-run pinch hit homer to power his team — Tigres de Licey — past Puerto Rico’s Leones de Ponce, 2-1. The Mets would love to get Martinez to the majors, preferably sometime this summer, but the 20-year-old’s body just doesn’t seem to want to cooperate.