Just a general note on defensive stats.
The -3 DRS and -0.4 UZR recorded so far have happened. Abstract stuff goes into it, but they do take real inputs and describe things that have occurred on the field. Brett has cost the team three runs compared to the average third baseman given the oppurtunities he's received by DRS, and 0.4 runs by UZR.
It's exactly like how he's posted a -5.0 wRAA on offense. Neither that nor his defensive stats reflect his talent, but both are credible numbers that reflect what has happened in the first 9% of this season. Both offensive and defensive performance is subject to great variance, and over a large sample it balances out. I hate it when people say "defensive stats cannot be trusted in small samples." Neither can anything other than Ks and BBs for pitchers, really. And those still take some time to balance out.