People often ask why things such as the NFL combine, the Senior Bowl, the East-West Shrine game and all the pro days are so important. A guy like Lane Johnson of Philadelphia is a good case study.

Johnson wasn't drafted No. 4 overall in April because he was the picture of perfect technical ability as a left tackle during his final season at Oklahoma. This is a guy who actually played quarterback at the college level before he eventually found his way to offensive tackle. And when you evaluate players on game tape, the sample size is smaller than you think. For instance, how many games did Oklahoma just dominate inferior competition? Maybe a handful. And how many times did Johnson get to face a pass-rusher who we'd consider NFL caliber? That number shrinks again. You look for consistency and growth, but week to week you look more for traits as much as dominance, because matchups and competition limit how much you can really take away from the tape. It's why the added evaluation plays such a key role.

Johnson's sample size was limited, and it was almost a given that he'd struggle some as a rookie still learning the nuances of playing tackle, actually moving positions and also getting comfortable in a new scheme. Over the past few weeks, however, we're seeing him put it all together. A whole NFL season can be a bigger sample size than even a few years of starting at the college level in terms of useful evaluation, and it's fun to see gifted players make major strides as they figure things out well into their rookie campaigns.

Again, the usual parameters:

• The rankings reflect play over the whole season, not just the previous Sunday.

• Positional value matters, but overall performance and impact on the team matter more.

• I do ask: Would this player be a starter on most teams? (I think that hurts QBs some.)

• Total snap count matters. Staying on the field is important because you get taken off to conceal weaknesses.

With the rules in place, here we go. This week, I've ranked a total of 30 and included a number of others I've noticed.

Alonso

1. Kiko Alonso, ILB, Buffalo

If you graded it only on per-play impact, you'd probably put Alonso lower on this list -- not far, but perhaps behind the next two players. But when you factor in the total impact of a player who is second in the NFL in tackles, has been as good as almost any linebacker in the NFL in coverage and literally never comes off the field, you give the slight edge to Alonso. He is a second-round pick who has played to the level of what you might hope for from a top-10 pick so far. At least I would, which is why he stays at No. 1.