Not to harp on the subject but after the last rounds of cuts (which included Rendon! Shocking as it may be that the guy with the most perfect swing in the world, who makes baseballs rocket off his bat in defiance of all laws of physics, is not ready for the major leagues.) The Nats in general, and Johnson specifically, were effusive in their praise for Corey Brown.
You might remember Corey as the other guy in the deal for Josh Willingham. The guy fans were less enthused about. He had hit .320 / .415 / .502 in AA in 2010 but it was only 90 games, he was admittedly old (24) for the league, and in AAA (though only 40 games) he immediately struggled with a .193 / .253 / .378 line. Last year was supposed to tell us what kind of player he really was and he put up a .235 / .326 / .402 line. So there you go. But wait! That's only because he sprained his ankle! and then put to much pressure on himself! And then had a staph infection a mere (1,2,3,4) 5 months later! And the locusts! Don't forget about the locusts!
Corey's time in camp impressed the staff but all it was was a good week and a half of baseball. Only 17 at bats to look at. Of course if he keeps hitting .400 the Nats won't have to look for a CF, but history tells us he won't. Corey Brown has had a handful of seasons in the minors. 1821 at bats to be precise. He has proven himself to be a middling average, good but not great power hitter, with ok patience. He fields well but strikes out too much. That latter is a problem because guys that strike out too much in the minors tend to strike out WAY too much in the majors. If he can control his strikeouts he might be a decent bench player or 4th OF for a couple years. But he needs to make the improvements now because over the next couple of years the adjustments will become harder and harder to make as his body starts to feel the effects of age.
There's a reason Justin Maxwell isn't anchoring the Nats outfield. It's the same reason you may not see Corey Brown back in a Nats uniform this year. They just aren't good enough.