I would be nervous about Lowell as a full time 3B, which is what you're asking. I'd be more concerned about the chance of a breakdown than the chance of poor performance when healthy though. those who enjoy baiting me might insist otherwise, but that's not really much different from how I felt about him last year.
His bat can cover for some of his defensive sins if his range can't bounce back at least a little, and he still positions well and has a cannon arm. The heightened risk of breakdown is the big problem with Lowell's trade value IMHO.
The reason I thought the Phillies might be interested is because they have a good defensive 3B who can split time with Lowell and take some of the weight of his defense off the team if he can't bounce back. Feliz represents a good insurance policy while Lowell represents a strong offensive upgrade.