What is the point of signing Kolarov ? He was just above average on both ends of the pitch when I watched Serbian games. I didn't follow him in Lazio(?), but as soon as I've heard about his possible Madridcoming I've been following his appearances and I've gotta say that Coentrao would be much better option for this position. Young, at least average in defense, really good in offense, proved himself against the best team in Europe(World?) during WC, didn't deny possible transfer to Real. The only problem could be his new 5-year deal with the club and it might take a reaaaaaally big amount of cash to get him to come.
+ Arbeloa is very solid in defense (except when he faces a fast runner like Messi, but well, who can stop Messi 1 on 1?), he can't play with his left foot though and personally, for me that would not be enough to kick him out of first 11, but if people want a proper left back then so be it.
Myself I'd put someone in midfield who is all offensive and would take a load of Alvaro so he can do his job in defense, possibly Marcelo or Di Maria (even though I don't really like the idea of putting him in central-left mid).