It would also depend on how far in the 3rd baseman had to come in or was playing when he fielded the ball. If he charges the ball(and you didn't say how hard it was hit) and threw off-balance or side arm, the angle could carry the ball down the left field line. If this is the case, he'd get to second but the left fielder, as long as he saw what was going on, should be setting himself in-line with the throw, should it get past the first baseman, thus keeping the runner honest. If the groundball was to short or second, the story is different.
Just my take on the possibilities here.

__________________
Fidel Montoya
Asahi2 Baseball Commissioner(Historical League Since 2004)
www.allsimbaseball.com (Hosting for OOTP with LIVE Online Tutorials)
Share Your Mods - Free, unlimited and easy to upload to share your Mods instantly(free site registration required)