With Jaguars running back Maurice Jones-Drew not reporting for training camp, the Jaguars had a roster spot that isn’t being used. So they shifted Jones-Drew, as expected, to the reserve/did not report list.
He can be removed from the list whenever he shows up. As long as he shows up by the Tuesday after Week 10 of the regular season, he can play this year and get credit for a year of service under his contract.
The point, then, is that the Jaguars wanted to use the roster spot on someone else. They used it on fullback Will Ta’ufo’u, who becomes the team’s fourth fullback.