Actually he did well on the metrics, but he defintely had problems out there.
I saw him play A LOT of outfield in Chicago. In 7 years, he never learned how to play the wall at Wrigley. He had a stretch of the Yips back in 2008-2009 where he kept dropping routine pop flies. For some odd reason, he added this little hop-step as he settled under them, and timed it so poorly that he it lead to him flummoxing the whole play. It got so bad, I was at a game where he caught a routine fly ball, and the crowd gave him a mock standing ovation (which he took in stride and tipped his cap).
However, as he was a former shortstop in Japan, he did have a great arm. And because he had some issues fielding the ball, runners routinely challenged him, so he did rack up a decent amount of outfield assists. Of course, for every runner he gunned down, a whole bunch more made it safely...