And we're off once again. For the past few seasons, I've been ranking the rookies, a true test of patience for me -- notice how they aren't in the same order as the final Big Board before the draft. But it's a fun exercise, because as we see over and over when it comes to rookies, it's not just about talent, but about fit, need and how quickly players develop according to plan.

Here are the parameters, same as always:

This is a measure for all games this season, not just last week.

Total snap count matters. Staying on the field is a measure of value.

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

Relative value matters. I ask: Would this player be a starter on most teams or on a good team?

Here's my latest ranking of the top 20 rookies in the NFL.

1. Marcus Peters, CB, Kansas City Chiefs

Heading into the draft, I wrote: "On tape alone, he has an argument as the top cornerback in the class." Peters looks like it so far. He has an interception in each of his first two games, including a pick-six against Peyton Manning in Week 2. So far, so good.

2. Marcus Mariota, QB, Tennessee Titans

The Week 2 loss in Cleveland was a step down from his Week 1 explosion against Tampa Bay, but Mariota has a 6-to-zero TD-INT ratio,and has already dispelled any notion the Titans are starting him only because they need to justify the high pick. He belongs.

3. Mitch Morse, C, Kansas City Chiefs

I knew the Chiefs were interested in Morse going into the draft, but I can tell you they had him rated a lot higher than I did. This is a case of them seeing a perfect fit, and Morse has looked the part of a veteran through two games.