3rd-and-short-to-medium situations tend to be man-coverage downs for the defense. As a result, offenses like to dial up their man-beaters. Among those are route concepts with shallow crossers coming from the perimeter and inside routes creating traffic for defenders to have to fight through.
Defenses must be ready to account for these concepts. One way to do so is by cutting the crosser.
Essentially, it’s a trade-off of receivers in man coverage that gives the defense better angles on the crosser. It also isn’t always easy for the quarterback to recognize pre-snap that the defense is planning to cut the crosser, which adds to the effectiveness of the approach.
This first example is from the 2020 NFC Championship Game between the Buccaneers and Packers. This was a 3rd-and-5 in the 4th quarter of a one-possession game. Tampa matched up in 2-man coverage (2 deep safeties, man coverage underneath):
The Packers were running a mesh concept with Allen Lazard running a shallow crosser underneath both the #2 receiver next to him and the crosser coming from the other side of the formation:
Focus on Buccaneers safety Andrew Adams and cornerback Jamel Dean at the bottom of the screen: