Noel held his own against much stronger players. That Ole Miss game was a marvel, and he did his work against some powerful bigs when he was in foul trouble. Speed and length and leaping ability go a long way to covering up for a lack of strength. But mainly, it's just about Noel's aggressiveness and ability to anticipate the game. He's a very aggressive defender for such a skinny guy. He's fearless.
A couple of things.
First, Noel being able to check a guard in college is a little different than checking guards in the NBA. Ask pretty much every big man ever.
Second, defense and rebounding aren't what the Wizards really need. Offense, offense and more efficient offense has to be need 1, 2 and 3.
I'm not saying I'd pass on Noel if he's there and Porter is gone, I'm just talking about needs for the Wiz given their current roster makeup for next season.