Sentence:  An observant base runner checks the outfield defense and easily goes from first to third when the batter hits a <WSD>flare</WSD> to right field. A base runner who does not observe the depth of the outfield must turn to watch the ball, see it drop, and then run. He probably doesn't make it to third base. 
Meaning of the word marked with <WSD> tags:  A low fly ball that is hit in the region between the infielders and the outfielders.