Well I finally read through this entire thread, and I have a few thoughts...
a) Why not have Mueller play second, Youkilis at third, and Bellhorn on the bench. He'll be extremely valuable as a switch hitter off the bench, and he has a better chance of getting on than Ramon Vasquez. He may even be a better defensive replacement than Vasquez...even at shortstop...who knows.
Keep Bellhorn for the season regardless. Like RSR said, we pay him very little (actually, 2.75 mill, which is more than I thought). He's valuable.
c) Some current updated stats for argument's sake.
Mark's batting .249, ranked 18th among major league second basemen.
His OPS is .723, ranked 16th among second basemen.
His 71 Ks are ranked first among second basemen, his 34 walks are second.
But possibly the most revealing stat, considering he's a #9 hitter:
His OBP of .362 is ranked 7th.
Discuss.