Florida Gators starting running back Montrell Johnson left the Florida-Tennessee game in the third quarter with an apparent lower-body injury. Senior quarterback Graham Mertz was also helped off the field on the same drive after throwing a touchdown pass to Arlis Boardingham. The senior running back was hip-drop tackled at the end of a 20-yard rush and was unable to get up right after the awkward tackle. Johnson was helped off the field by trainers and was seen trying to get his leg loose on the sideline. Mertz went down shortly after Johnson’s injury. The senior threw a touchdown pass to Arli…