Jefferies has spent most of his life in great pitchers parks in the NL; an average pitcher would have an ERA of 3.80 in those parks, and he's at about 4.10 while in the NL. And he got his *** absolutely handed to him in a neutral, AL environment. His sample size for you is very small; his ERA will be over 4 by the end of the season unless you have a monster defense.
Belliard has all of 34 major league innings under his belt; his ERA will go up near 4 by the end of the season, also. That said, his very low VsL is substantially protected by his being a reliever, since simmy does a worse job of getting the platoon advantage midgame than humans do in the startling lineup.