MJD, who is the still the Jaguars leading rusher, hasn't played since suffering an injury on October 21. For some reason, the Jaguars never placed him on IR, so he remained on the roster.
Long was the Chiefs seventh round pick in last April's NFL Draft. He was on the practice squad and this is the time of year when you see teams swiping other team's practice squad players so that they can have their rights for the upcoming offseason.
Long could have chosen to stay on the Chiefs practice squad but he gets what appears to be a better opportunity on the Jaguars 53-man roster.