A one on one pass rush in Football is a defensive pass rush strategy in which one defensive player is responsible for getting around one offensive player when rushing the quarterback, and one offensive player is responsible for defending against one defensive player when guarding the quarterback. One on one pass rushes usually occur at the end of the line of scrimmage between defensive ends and offensive guards.
When a one on one pass rush occurs, it's usually for one of two reasons: the offensive team is confident in the ability of the offensive lineman to defend against the defensive rusher, or the specific play that the offense is running leaves the offensive team shorthanded on the line of scrimmage, requiring a one on one situation. If the offensive team can avoid a one on one, they will often take that opportunity as an advantage to defend against the pass rush.
For a defense, having an elite player at the defensive end position can be a huge asset due to how often one on one pass rushes can occur at the end of the line of scrimmage. JJ Watt, defensive end for the Houston Texans, is considered one of the best pass rushers in the NFL.