This week at the New York Times, a look at the Patriots trick formations, and how New England has creatively worked around the NFL’s rules on eligible pass receivers.

In the divisional round of the N.F.L. playoffs, the New England Patriots dived deep into their playbook for a series of trick plays. What the Patriots did surprised even rule book aficionados, to say nothing of the team’s opponent, the Baltimore Ravens. It was also entirely legal, and the result of Coach Bill Belichick’s limitless ingenuity and deep understanding of the N.F.L. rules.

The N.F.L. publishes a rule book each year titled the “Official Playing Rules of the National Football League.” Rule 7, Section 5 of the 2013 edition covers eligibility. It is that section that contains one of the most basic elements of N.F.L. play, a rule so commonly adhered to that it goes unnoticed by most observers: There must be at least seven players on the line of scrimmage at the snap of each play.

Of those seven players, only the two outside players are eligible to catch a pass on a play; the inside five players on the line of scrimmage are, by definition, ineligible. But not only are the two outside players the only ones on the line of scrimmage eligible to catch a pass, those players must be eligible receivers.

You can read the full article here.