What is the outcome when R1 collides with F4 while he fields a ground ball and all bases are occupied?

When R1 collides with F4 while F4 is attempting to field a ground ball, the play results in the ball becoming dead. This scenario typically falls under interference rules, which state that if a runner interferes with a fielder's opportunity to play the ball, the ball is ruled dead. In this context, because all bases are occupied, the outcome alters the players' advancement on the bases.

The interference by R1 not only prevents F4 from making a legal play on the ball but also means that the ground ball is no longer a viable part of the play. Therefore, to maintain a fair game and address the interference, the umpire calls the ball dead and determines the appropriate consequences based on the interference rules. Given the situation with all bases occupied, the result is not simply a continuation of play, as would be expected in a situation where no interference occurred.

This understanding of interference effectively clarifies why the established ruling requires the ball to be dead in this instance rather than allowing play to continue or differentiating the outcomes for individual runners.