A player's break from either backpedaling or a complete stop is infinitely more important than what a stopwatch measures. Besides, he's a junior and has yet to fully develop physically.
I'll ask this question, although it's a baseball analogy. What's more desirable for an infielder:
1) His ability to react quickly to the ball and cover a lot of ground being able to dive and make a play, or
2) His ability to know the hitter's tendencies, what the pitcher is throwing, what the situation is, and align himself close to where the ball will likely go BEFORE the pitch is even thrown?
The best lineman I ever coached was a guy who might have run a 5.5 in the 40. His acceleration from a three-point stance was simply phenomenal, and his focus on technique (and geometry) allowed him to compensate for his complete inability to actually pursue a player downfield. As a sophomore I'd have taken him over any other lineman I coached....as he developed more physically, he became a tremendous presence on the field and ended up being first-team All-Ohio. It was his focus on the "minor things" early on that allowed him to blossom, stopwatches and measuring sticks be damned.
lol: 
