Pirates Prospects explains why some fans don't trust Neil Walker's strong performance even thought they trust Jose Tabata's. Essentially, the issue is that Walker had a terrible year and a half in Class AAA from the beginning of 2008 through the middle of 2009, whereas Tabata has been fairly consistent throughout his career, so it's easier to believe he'll be able to sustain his performance.
↵As a big proponent of the importance of minor-league numbers, I was one of the big Neil Walker skeptics a year ago, but even I am coming around. He's been sustaining a high level of performance for over a year now, including a .310 AVG / .354 OBP / . 486 SLG line this year, and he looks very convincing at the plate, posting a 24.4% line drive percentage that would be among the best in baseball if he had enough plate appearances to qualify for the leaderboards. His batting average might come down a bit next year, but if he keeps hitting the ball hard, he'll be a valuable everyday player for years to come. That's a big leap forward for a guy who was aspiring to be a utliityman a few short months ago.