I'm not sure where you get speed would have helped on your TDs.
TD 1:
http://goallineblitz.com/game/replay.pl?game_id=597788&pbp_id=6104361Not speed. You'll notice that at around the 11 yard line your cb has trouble adjusting to the route. He does a little stutter step, then chases the wr. That is agility. First he has to adjust (it looks like he's changing from his back peddle to running alongside the wr), then he has to accelerate out of that change. You'll also notice that he makes to to the wr, but overruns him slightly, and can't cut back to stop the pass. That is also agility.
TD 2:
http://goallineblitz.com/game/replay.pl?game_id=597788&pbp_id=6107483Not speed. Your cb is back peddling, sees the throw, and breaks on it, but can't change direction fast enough or accelerate fast enough to get to the wr and stop the pass. Once again, this is agility.
What are your change direction and shutdown coverage at?