With the big league team presumably desperate to contend with Trout 'just' entering his prime years - the Angels need to fill some big holes sooner than never.
With injuries knocking out starting pitchers left and right for much of the year [and maybe through next year] - the team was forced to start guys like the corpse of Tim Lincecum, Ghoulish Chacin, something called a 'Brett Oberholtzer' and Jeff Weaver.
The obvious problem is every other team looking to get Quintana or Sale has a deeper set of prospects to trade off - maybe outfield prospect Jahmai Jones, a couple of pitchers [Nate Smith and/or Grayson Long] and money is just not going to get anything done.
Finally the Angels probably need a competent veteran catcher - after Geovany Soto didn't play much due to injuries, Jett Bandy did emerge as a viable semi-regular option while Carlos Perez kind of plateaued as a strictly a backup guy with limited upside.
A caveat is McCann is going to be 33, an age where many catchers seemingly crater with the bat - will the Angels be able to give McCann time at DH [Pujols] or first base [C.J. Cron] to get his bat into the lineup when he's not catching.