With runners on first and second and no outs during the third inning in the rubber match between the Padres and Rockies Sunday, Padres outfielder Carlos Quentin sent a grounder to slick-fielding Rockies third baseman Nolan Arenado. The result was, eventually, a triple play:
Rule 7.09 states that it is interference by a runner when ...
(e) If, in the judgment of the umpire, a base runner willfully and deliberately interferes with a batted ball or a fielder in the act of fielding a batted ball with the obvious intent to break up a double play, the ball is dead. The umpire shall call the runner out for interference and also call out the batter-runner because of the action of his teammate.
We often see runners go a bit away from second base in an attempt to break up a double (or triple!) play, but Seth Smith was pretty far inside the bag and his biggest problem was probably his arms being out. In fast motion to an umpire, that had to look like Smith attempted to grab D.J. LeMahieu's legs. That's always going to be called interference.