I picked Nomar up just in case this trend continues.
I was going to say he's faced some pretty good pitching so far in August, but after looking at the box scores for the eight August games in which he went 0-fer, it simply isn't true. Prior, D. Willis and Harang (maybe) are the only really good starters he's faced in those 8 games. There's also been a lot of runs scored in those games.
To answer your question, yes. I'm worried. Especially with the playoffs coming up in just over two weeks. Nomar is looking pretty good so far, so I'm not sweating just yet. I wouldn't drop him either, if I were you, but I would definitley be looking at acquiring a plan B.