We are just starting the season and I have to fill my CF spot. I'm going to try to sign or trade for a guy but if not, I might have to settle for one of these two guys.

a style="color:black;" href="http://www.whatifsports.com/hbd/Pages/Popups/PlayerProfile.aspx?pid=3103672" target="_blank">John Gibson</a>

or

<a style="color:black;" href="http://www.whatifsports.com/hbd/Pages/Popups/PlayerProfile.aspx?pid=3666301" target="_blank">Juan Posada</a>

While neither will be an everyday player, which would be better in a backup role? I'm leaning toward keeping Posada in AAA for another year, since it's only his 3rd year and I think he still can boost his ratings a bit with regular play, whereas I don't think  Gibson will improve too much more.

Additionally, I may have to move one of my other position players to CF. While I know neither will win a GG, which of these 2 would be a better defensive CF?

<a style="color:black;" href="http://www.whatifsports.com/hbd/Pages/Popups/PlayerProfile.aspx?pid=3243548" target="_blank">Carlos Valentin</a>

<a style="color:black;" href="http://www.whatifsports.com/hbd/Pages/Popups/PlayerProfile.aspx?pid=1424388" target="_blank">Davey House</a>

Thanks in advance.

Posada will eventually be the best defensive CF, but his offensive #s are not very good.  Have you thought about platooning CF, with one guy playing vsL and another playing vsR?  I really like Gibson as a vsL platoon.  You might test the FA market to see if you can find a cheap guy ($1-2mil) who is worthless vsL but can hit right-handed pitching and play him alongside Gibson. 

I believe defensive requirements for CF are 85 glove and 85 range, but it seems to me that the game engine is more forgiving of a sub-par glove at CF than it is of a sub-par range.  For my part, I wouldn't even think of playing a guy with less than 80 range in CF.

Use the crappiest one.  Field free to use that advice for the rest of your lineup :)

With 25 power, 14 contact, I don't think Gibson will ever crack .700 OPS in the majors. And he will be below-average as a CF. So basically, he's terrible. Posada sucks slightly less but is still pretty terrible.

I would definitely play House or Valentin over either of those. Probably House. I would probably pull Posada up after 30 games so as not to burn his arb clock and use him as a defensive replacement and see if he develops more.