In MLB, can a pitcher face toward a runner as though to prevent a steal, then immediately throw a pitch?

In MLB, can a pitcher face toward a runner as though to prevent a steal, then immediately turn and throw a pitch, or would that be considered a balk? I ask because I was watching a high school game where the ump let this go... I know the rules are different, and I'm not really concerned with high school rules or if this was a good call, I was just wondering if it's legal in MLB. Thanks!