Exactly. Combine numbers really only establish an athletic baseline. I've always maintained a couple tenths difference in 40 times is almost meaningless in itself. Football speed is not the same thing as sprinting down a straight track. Of course there are those freaks that are both lightning fast sprinters and have elite football speed, but they are rare.I just made another post where I answer all those questions.
Keep in mind - play on the field trumps combine information - LOL
Tim Brown, for example, was one of the fastest players in the NFL at one time, but didn't become a great receiver until he developed football skills. Many very "fast" guys never make the grade, while some who were seen as slow by comparison kicked butt on the field.