Runners on 2nd base (R2) and 3rd base (R3) and one out.  The batter (B1) singles to right (and leaves his bat in fair territory about 2-3 feet up the 1st base line). B1 is easily safe at first and R3 easily scores from third base -- BUT -- it is going to be a close play at home as R2 attempts to score from 2nd base.

 

The right fielder relays the ball to the 1st baseman. The 1st baseman is about to fire the ball to home to attempt to retire R2 -- HOWEVER -- R3 is standing 2-3 feet in front of home plate picking up B1's bat (remember the bat from earlier in the play?)!

 

The 1st baseman does not throw home because, in the umpire's judgement, R3 was standing in the way. Is there any umpire action on R3 or R2 or B1 on this play? Does it matter that the 1st baseman did not throw the ball?