I've spent quite a bit of time today battling in order to level a few specific pets, and have seen a distressing trend. In several battles (more than one in five, in fact) what starts out as a green or blue opponent drops in quality before the fight starts. Usually to poor. Does anyone know what triggers this?
When you first load a pet battle it can show the color and stats from the last pet you battled before switching over to what the new pet actually is. You're not losing out, it's just taking a moment to show you the real information.
I learned my lesson from forfeiting some battles where I got a rare of the wrong breed but seeing it update to the one I wanted as the battle closed out. D'oh! Anything close I always let it sit a second now.