If you don't like math, then I'll give you the summary: those of us who looked at Devon's catch as evidence that he isn't very fast (I'm included in that group) were wrong. That catch is actually evidence that he is very fast. Maybe not 4.3 fast, but definitely sub-4.5.

How did I arrive at this conclusion? The AFR freeze on the play when Devon caught the ball showed that Blanding was 10 yards away from him when he caught the ball. However, Devon was at the 41, while Blanding was at the 39. Thankfully, the Pythagorean theorem lets me know that since Blanding was 10 yards away from Devon, and Devon was 2 yards farther upfield, that means that Blanding was 4 times the square root of 6 yards (about 9.8 yards) to the left of Devon. That freeze frame also makes it clear that Devon had slowed almost if not completely to a stop to catch the ball, while Blanding was close to full speed.

Moving further ahead in the clip, Blanding pulls vertically even with Devon before they get too far into BYU territory, but judging from when Devon starts to weave slightly away, it's clear that Blanding would have caught him between the 35 and the 30, likely closer to the latter. Let's say the 32. That's 27 yards upfield from where Devon caught the ball. Again, using the Pythagorean theorem, I can see that Blanding ran 30.6 yards in the same amount of time that Devon ran 27 yards. But again, Blanding was basically at full speed at the start of that run, while Devon was basically stopped.

As others have pointed out, Blanding was either the #1 or #2 safety prospect in the country last year. 247sports has his 40 time as 4.50, while Rivals has 4.55. So from a near or complete standstill, Devon ran 27 yards as fast as a 4.5 40 guy already at top speed ran about a sprinting stride (probably slightly less) farther.

QED