Well as the sim is mainly a mystery to us we can only guess, but here is my guess.
The QB was hurried, your guy might have had to slow down to catch the ball (what is your vision?).
First step doesn't always fire.
The CB most likely had closing speed, so he was able to close up to 5 yards from your dot in relatively short order.
The CB most definitely has Ball Hawk, which gave him a boost to AGI, VIS, and SPD after the throw and before the catch which allowed him to speed up to a faster speed (than normal) while your dot was slowing down to make the catch. And then Closing Speed would've allowed him to maintain the elevated speed while your dot was still just starting to run.
It was the 4th quarter (and 4th down)... your dot may have been exceptionally tired that play. Your dot was in all plays in that drive, and he was in the last play of the drive before that.
Your team was losing, confidence may have been an issue.
Without knowing your dot's vision I would suggest more. Although you might have enough already... but who knows, your dot will never always perform at 100% of what you expect him to, and sometimes they will F up, even though there is nothing you can really point to in the build... that's just the way the sim is, it is a Random number generator after all.
