2:35 PM PT -- Nick Piazza -- the NFL official who went down with an injury following the collision with Alvin Kamara -- suffered a dislocated knee as well as a fractured fibula.

But, thankfully, his blood vessels remained intact, according to New Orleans Saints writer John DeShazier.

DeShazier added that surgery for Piazza is likely to happen next week.

An NFL official had to be taken off the field on Sunday on a stretcher ... after he suffered a gruesome leg injury following a sideline collision with Alvin Kamara.

The play happened in the second quarter of the Saints' matchup with the Lions in New Orleans ... when Kamara took a pitch from Derek Carr and accelerated toward the first-down marker.

On his way, though, a Detroit defender shoved him out of bounds ... and when he went crashing toward the turf, his momentum carried him right into the knee of a game official.

The sideline worker crumpled in pain as soon as Kamara hit him ... and broadcast cameras showed his leg had bent awkwardly inward as a result of the hit.

Trainers eventually raced to his aid ... and strapped him to a backboard -- before carting him away from the field for further treatment.

The NFL has not yet released an update on his condition as of Monday morning.

Kamara and the Saints, meanwhile, were able to try to mount a comeback despite the gruesome scene at the Superdome ... but they ultimately lost to Detroit, 33-28.