The NFL instituted a new rule this offseason to make it easier for teams to carry extra depth at quarterback.

But the Patriots can't utilize it -- at least, not with how their roster currently is constructed.

The league released an explainer Monday detailing when its new emergency QB regulation does and does not apply. For a team to dress a third signal-caller and have him not occupy a gameday roster spot, all three quarterbacks must be on that team's 53-man roster.

New England currently has Mac Jones and recent waiver-wire pickup Matt Corral on its 53 and Bailey Zappe on its practice squad. The Patriots can temporarily elevate Zappe to serve as Jones' primary backup for this Sunday's season opener against the Philadelphia Eagles -- each practice squad player gets three such elevations -- but they cannot do so and also take advantage of the new third QB provision.

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The only way to dress Jones, Zappe and Corral under present circumstances would be to give all three spots on the active gameday roster, which the Patriots rarely do. For instance, when the Patriots had three healthy QBs on their 53 early last season, they made Zappe a healthy scratch.

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The Patriots also could make use of the rule if they officially promoted Zappe, who was waived on cutdown day, back to the 53-man roster. But that would require them to remove another player.

It's unclear whether teams were informed of this stipulation when the new bylaw was approved back in May, but the initial verbiage made no mention of the first- and second-string QBs needing to be on the 53-man roster.

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Here's how the rule read at the time, via NFL.com:

One hour and 30 minutes prior to kickoff, each club is required to establish its Active List for the game by notifying the Referee of the players on its Inactive List for that game. Each club may also designate one emergency third quarterback from its 53-player Active/Inactive List (i.e., elevated players are not eligible for designation) who will be eligible to be activated during the game, if the club's first two quarterbacks on its game day Active List are not able to participate in the game due to injury or disqualification (activation cannot be a result of a head coach's in-game decision to remove a player from the game due to performance or conduct). If either of the injured quarterbacks is cleared by the medical staff to return to play, the emergency third quarterback must be removed from the game and is not permitted to continue to play quarterback or any other position, but is eligible to return to the game to play quarterback if another emergency third quarterback situation arises.

Head coach Bill Belichick on Monday said he had not decided whether Zappe or Corral would open the season as the QB2. Corral, a Carolina Panthers third-round draft pick who missed his entire rookie season with a foot injury, made his Patriots practice debut Monday afternoon.

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