See Defence - Villanova 1-2-2 3/4-court.
The 1-1-2-1 basically looks like the 3/4-court 1-2-2 (red), but is a more conservative press. Drop back into a 2-3 zone (instead of man to man), with X1 and X2 at the top.
X1 - pressures the ball when it comes in.
X2 - no middle, below the level of the ball.
X4 - ballside, nothing over his head.
X3 - weakside, gets to the midline, no skip pass over his head.
X5 - just protects the basket.
If the offence uses three guards to bring up the ball, X1 plays with his back to the middle of the floor, forces a pass to the sideline, keeps the ball out of the middle. Never turn, open up, and get beat.
The guards work in a tandem. On a 1-2 pass, X2 hangs in there until X1 takes away middle, then X2 takes 2.
If 2 passes up the sideline to 3, X3 contains and fakes at 3, gives him space, X2 drops back and X3 drops back, into a 2-3 zone with X1 and X2 at the top.
The 1-1-2-1 gets more aggressive if the other team is not trying to attack, X3 and X4 step up, but X5 always protects the rim.