ESPN reporting M.Turner re-signs with Chargers

[Smashmouth24]

http://sports.espn.go.com/nfl/news/story?id=2850586
Technically, a trade for Turner might be facilitated now that he has signed the one-year deal with the Chargers, because a player must be under contract to be dealt.

Is this true? What do teams do with franchised players that they trade but haven't signed the tender? They have to fit the multi-million dollar cap hit into their salary cap before completing a trade? That makes no sense.