A longstick joins a slow-break or fast-break. Nothing comes of the break. The longstick jogs off the field, ostensibly to be substituted, and usually followed closely by Team A's offensive midfielder who realizes he does not want to play defense.
Once the longstick steps outside the offensive box, however, he stops. Unsure, Team A's offensive MF stops too.
This is the "55," or "five-on-five," scheme. Duke uses it at least once or twice a game. The object is two-fold: To create a little more space for the offense and to try and keep Team A's offensive midfielder on the field to play defense.
It has its roots in the NBA. In the early 1980s, when zone defenses were illegal, current Warriors Coach Don Nelson devised a scheme by which his worst offensive player was stood at midcourt on offense. The defense had to have someone defend him or else it was a zone, i.e. an "illegal defense." This not only kept Nelson's worst player from the ball, but the 4-on-4 gave his offense a lot more space to operate. (fwiw Nelson was coaching Milwaukee at the time.)
Against "55," Maryland and Georgetown didn't defend it as such; they kept the offensive midfielder next to the longstick until the longstick left the field. Non-money bet says Johns Hopkins will sag it's offensive player into the defense and take its chances there rather than giving the extra space for a 5 on 5.