For this post, I'll focus just on the concept of the double-relay and offer some tips on what is expected from each of the two players involved.
What is a double-relay?
A double-relay is where both the shortstop and the second baseman go out into the outfield to be the relay men for balls hit deep. They line themselves up with the outfielder who is throwing and the base to which they will be throwing. It's usually only seen on a possible triple or when a ball is driven to the fence with runners on who may now have a chance to score. The throw from the deep outfield position all the way to home plate would require a double-relay. One middle infielder acts as the lead guy and the other one acts as the trailer. You'll usually see a double-relay when balls are hit anywhere from deep right-center to deep down the left field line. Balls hit down the right field line are covered below under "Variations."
Why the double-relay?
The double-relay works because it accomodates both good and bad throws by the outfielders. If only one player went out to be the cutoff man, nobody else would be around if the throw to him went over his head or just got past him. Having two players there allows good throws to be relayed but also provides back-up in case the outfielder's throw is not a good one. Having the second player as a trailer also helps with communication since the lead guy watches the ball and the trailer watches the runner(s) and communicates to the lead guy where the ball should go.
Who leads and who trails on a double-relay?
There may be an exception here or there but basically the shortstop is the lead man on all balls hit to the left side of the field (from centerfield to the left field line). The second baseman becomes the lead man on balls to the right side of the field. If the ball is hit directly over the center fielder's head, usually the player with the better arm becomes the lead guy. That should be worked out in advance between the two players but they still may have to communicate on the fly as needed.
How do they both position themselves and why?
The lead guy on a double-relay goes out far enough so that the outfielder can reach him in the air with a strong throw. This requires some prior knowledge of how good the outfielder's arm is. If he has a strong arm, the lead guy will not have to go out as far. A weaker arm would require the lead man to move a bit farther out on the play. The trailing player in a double-relay has a more difficult job because he is doing multiple things at the same time. He's helping to line up the lead guy if needed, he is watching the play develop in the infield so the lead guy knows where to throw the ball after he gets it, and he has to watch for bad throws from the outfielder. To do all this most effectively, he should position himself about 10 feet away from the lead man. As he runs out to be the trailer, he'll need to peek back to the infield frequently to see where the runners are in the process of rounding the bases.
On this ball hit to deep right-center, the second baseman (4) and the
shortstop (6) set up a double-relay for a possible throw to home plate.
To learn more about the proper body position of the lead man, click HERE. This previous post dealt with how first and third baseman position themselves before and after the throw by the outfielder when they are cutoff men. The principle is the same for the lead man on a double-relay.
A possible variation of the double-relay occurs on a ball hit all the way down the right field line. In this case, some coaches do not want the shortstop to run over to that side of the field to be the trailer. If the ball was hit to the right field gap, then the shortstop is the trailer but usually not on a ball hit down the right field line. On a ball down the line, many coaches want the first baseman to be the trailer since he is already on that side of the field and doesn't have much to do. This also frees the shortstop to cover a base if needed on the extra base hit.
Another variation would involve the configuration of the outfield fence. On some fields, the fence in a particular part of the field might be very short. Balls hit to that part of the field might not warrant a double-relay because the outfielder gets to the ball and gets rid of it before both middle infielders would have a chance to get set up.
The double-relay may sound a bit complicated but once practiced a few times, it becomes fairly easy for players to do. The biggest key is getting the players to be positioned correctly and then not being afraid to communicate as needed.