Part of his problem is that the 3B/LF/2B types have been hitting okay. Factor in the "pinch hit penalty" where guys tend to hit worse as pinch hitters than they do otherwise, and there just isn't as big of a need to pinch hit with him.
So now he's just rotting on the bench, not getting any reps, and then gets thrust into the lineup against a crafty veteran and looks like crap.
If they are going to use the 26th man this little, just cut the guy loose and sign Billy Hamilton. He's 22 of 23 on steals attempts the last 3 years and can succeed as strictly a pinch runner.