If Only by captainschmoop
Since the group is newly formed, Steve takes it upon himself, with a little nudging from Coulson, to try to get the gang more comfortable around each other - building up teamwork mentality and whatnot. When he sees Cap's efforts actually paying off, Loki decides to throw a curve ball their way by turning Steve back into his pre-serum body. While that doesn't stop Steve from trying to help others and his teammates, there's a deadly price to pay if it goes unchecked for too long.
(alt here: http://i.imgur.com/TM0Cj.png)