If the New England Patriots intentionally deflated footballs used in Sunday’s AFC championship win over the Indianapolis Colts, it wouldn’t have been as easy to pull off as it might seem.

NFL rules require each team to provide 12 primary balls to the referee for testing 2 hours, 15 minutes before kickoff to ensure they fall between the proper inflation limits of 12½ to 13½ pounds per square inch. The home team also must provide 12 backup balls, and the visiting team has the option to provide 12 more for outdoor games such as Sunday’s at Gillette Stadium.

The referee “shall be the sole judge as to whether all balls offered for play comply with these specifications” and the balls “remain under the supervision of the Referee until they are delivered to the ball attendant just prior to the start of the game,” according to Rule 2, Section 1.

A person with intimate knowledge of the process told USA TODAY Sports the ball attendant is a uniformed official – generally the same person each week at a given stadium – who comes to the locker room to pick up the balls and takes them to the officials’ locker room for testing.

The ball attendant delivers the balls to the ball boys – usually four provided by the home team and two traveling with the visiting team – who make sure their quarterback’s preferred balls get into the game, said the person, who spoke on condition of anonymity because they weren’t authorized to speak publicly.

At halftime, the balls return to the officials’ locker room, the person said. So, if proper protocol is followed, the only opportunity to manipulate the balls is minutes before kickoff or during the game on the sideline, where there’s a risk of anyone in the stadium and dozens of TV cameras seeing it.

Citing “league sources either involved or familiar with the investigation,” ESPN reported Tuesday night that 11 of the Patriots’ 12 game balls Sunday were underinflated by 2 pounds per square inch. The NFL and the Colts declined comment, and the Patriots reiterated they’re cooperating with the league’s investigation.

Asked how long it takes to change and measure the pressure of a football, the person said, “Ten seconds. But if they were all exactly 2 pounds under? It would be almost impossible to get them exactly all the same weight or the same psi.

“That, or you’d have to be really good at knowing exactly where to pull the needle. And then what if you take too much out? How are you going to pump it back up on the field? You can’t. You need a ball pump to do it. That’s what’s even more weird about it. Too many moving parts.”

The referee for the AFC championship game was Walt Anderson, who has participated in 253 NFL games since 1999 as a line judge and referee, according to pro-football-reference.com.

One indication something may have been amiss Sunday came after the opening kickoff of the second half, when more than 2 minutes passed before the Patriots’ snap. After an initial delay, Anderson signaled to start the clock and the Patriots went to the line – only for Anderson to blow his whistle moments later as a new ball was tossed in from the New England sideline.

Former NFL referee Mike Carey, working as an officiating expert on the CBS broadcast, speculated that officials may have inadvertently spotted one of the six new “K” balls that are unsealed from a special box by officials before the game, specially marked and used exclusively for the kicking game.

This isn’t the first possible ball deflation scandal. In 2012, the University of Southern California was fined and reprimanded by the Pac-12 Conference after it was discovered that one of the Trojans’ student managers had intentionally deflated game balls during a loss to Oregon. The university said then-coach Lane Kiffin, his staff and the roster had no knowledge of the deflations.