runner interference?

[Guest D- money]

Runner on second, no outs. Runner breaks to steal third while batter swings hitting a hard ground ball between the third baseman and shortstop. The third baseman, who had been playing even with the bag moves back and away from the foul line colliding with the runner who is attempting to reach third. The shortstop unsucessfully attempts a play and the runner touches third and continues onto score.  The defence wants the runner called for interference. 

[Richvee]

Did F5 have the best chance at fielding the ball? Or F6? The umpire must decide who is the protected fielder. Only one fielder, the fielder with the best chance at fielding the ball, is protected. 

If F5 did indeed have a play on the ball, being that he was in front of F6 with the first shot at fielding the ball, I'd guess he'd be the protected fielder, and therefore we have INT on R2. The play is dead, R2 is out BR gets 1B. 

On the other hand, if F5 had no shot at fielding the ground ball, (F5 just taking a casual step or two in the direction of the batted ball into R2's path), and F6 was obviously the only one with any shot at fielding the ball, then we would have obstruction on F5. Play continues with R2 being awarded bases the umpire deems he would have made safely had there been no obstruction.