I don't know if this is a bug, or a glitch, or a artifact of how the game engine is graphically displayed. I've noticed a few times that when a player breaks free and the defenders have to run him down that all of the players converge into one spot behind the runner. When they converge into this spot, they seem to cease accelerating. So a player that closes a 10 yards gap between him and the player carrying the ball won't ever get to the ball carrier.

Here's an example from a game in MFN-19: http://mfn19.myfootballnow.com/watch/1626#308276

The ball carrier is this guy (73 SP, 53 Carry): http://mfn19.myfootballnow.com/player/4169

The first two defenders that he out runs are these two -- CB (96 SP, 94 AC) and SS (100 SP, 94 AC):
http://mfn19.myfootballnow.com/player/4537
http://mfn19.myfootballnow.com/player/4607

Either one of the defenders should have been able to run down the TE. But once they converge into one space they stop accelerating. What's hilarious is more defenders catch up to only get stuck in the same spot a half yard behind the ball carrier.

That sucks!