That means that evaluating offensive and defensive linemen is almost impossible because it is in contact drills that you can see who's a player and who's not.
You can, however, get a gauge with the athletic ability of the skill position players, the accuracy of the quarterbacks and the pass-catching ability of the receivers and tight ends, among other things.
And what we saw this weekend wasn't particularly overwhelming.
We'll start with the bright spots.
Ricky Williams looks great. He looks quicker than he has perhaps at any time during his stay with the Dolphins.
How that'll translate to the field in the preseason and regular season, who knows, but it's clearly an encouraging sign.
At wide receiver, it's good to see Ted Ginn Jr. out there running. He looks maybe more decisive in his route-running than he did last season. The Dolphins need him to come up big next season because the receiving corps is very shallow (more on that later).
Joey Porter at linebacker looks like he's in tremendous shape, and he's impressed his coaches with the way he's been moving. He's a guy who might have a big year now that the Dolphins will be using him the right way (as in, pass-rushing outside linebacker in a 3-4 defense).
On the flip side, it would be great to be able to say that the quarterbacks look great, but they really don't.
As Sparano mentioned last week, they've taken turns looking sharp, but that also means they've taken turns looking way less than that. On Sunday, John Beck and Chad Henne looked particularly ragged in team drills.
In their defense, it's not like they have a tremendous receiving corps to pass to.
It seems we see a lot of dropped passes around camp these days. David Kircus, the former Detroit and Denver wideout, has drawn a lot of praise this spring but he's also dropped some balls.
The same goes for Derek Hagan, who just can't seem to ever make the really difficult catch. Hagan has talked about this being his breakthrough year now that Chris Chambers and Marty Booker are gone, but we just don't see the signs.
Among the tight ends, the one we want to see on the field is Anthony Fasano, but he's rehabbing his shoulder and sat out all the team drills over the weekend.
So, what did we learn this weekend? Not a lot we didn't already know. There is uncertainty at quarterback and the wide receiver position is a concern.