Would McCann for C. Davis/Shields be a big mistake?

[DSheppard]

This is a standard yahoo head to head league.

My current 1b is James Loney, who I drafted in the 16th round out of necessity after missing several targets, I really don't like him.
When salty was around in the 23rd round I went ahead and grabbed him with my mind toward trading mccann to sure up other problems.

My SP is pretty meh with Zambrano/Joba/Verlander/Garza/Cueto/Floyd.. Shields would help.

There are too many rangers involved for me to be objective.. could really use an outside opinion or two. I kind of suspect that everyone will say to keep the best player (mccann) and I just want to be sure.

WHIR if I have anything at all constructive to say.