We'll never know what the Eagles would look like had they drafted Russell Wilson instead of Nick Foles, but it is likely Chip Kelly would be using the zone-read more than he does now had Andy Reid drafted the Seahawks quarterback, as he intended.
Fact: Kelly does not need a mobile quarterback to win in the NFL. Fact: Kelly has successfully catered his offense to the skills of Mark Sanchez and Nick Foles. Fact: Kelly still employs the zone-read even though neither quarterback has proven to be much of a threat to run the ball.
It's still an effective play. It can be lethal, though, if the quarterback is athletic, a quick thinker, and smart with the football - like Wilson.
"He's just a great athlete," Kelly said last week as the Eagles prepared for their showdown Sunday with Seattle. "He has legitimate speed and quickness where he can burst off a disconnect and gain some serious yards. And he's a really, really good decision maker.
"It makes him a legitimate threat every time they are running the ball out of the gun, that the ball can be handed off or he can keep it."
Sanchez had never really been asked to run the zone-read until he came to the Eagles. He has admitted that it hasn't come naturally, but after several tentative carries in his first four games in place of the injured Foles, Sanchez had success against the Cowboys on Thanksgiving.
Kelly doesn't need his quarterback to run as much as Wilson (91 times) or gain as many yards (679), but several carries a game that keep defenses honest - Sanchez had three carries for 20 yards and a touchdown in Dallas - would add another element to what is already one of the NFL's most potent offenses.
Option football has not revolutionized the league as some suggested two years ago, when Wilson, Colin Kaepernick, and Robert Griffin III burst onto the scene. Griffin got hurt too often, and Kaepernick hasn't run as much this season or been as effective when he has.
But Wilson is rushing more than ever and with the highest per-carry average of his career (7.5), and the Dolphins, with former Eagles quarterback coach Bill Lazor running their offense, have effectively used quarterback Ryan Tannehill (6.4 yards a rush) in the zone-read.
According to numbers compiled by NFL.com, the Seahawks have had the highest percentage of zone-read plays (13.3 percent) this season, followed by the Dolphins (9.5), Eagles (7.9), Jets (6.3), and Panthers (5.9).
Some thought the zone-read would be more prevalent in the NFL by now, and the fact that it isn't seemingly has less to do with how teams have defended it and more to do with a lack of suitable quarterbacks.
But with college prospects such as Marcus Mariota, Jameis Winston, Brett Hundley, Dak Prescott, and Bryce Petty eligible for the 2015 draft, the next wave of dual-purpose quarterbacks could have offensive coaches utilizing the zone-read - with a caveat.
"It's going to be around as long as you have quarterbacks that don't get hit," Seahawks coach Pete Carroll said. "Our quarterback is really good at not taking shots and getting hit. There's very few guys that can withstand the rigors of getting hit if they're running on a regular basis."
Or few who are athletic enough to run but know when to ease up and avoid shots. Michael Vick had a running back's mentality and has never learned to give himself up and slide feet-first. Kelly recalled last season when Vick tried to block for LeSean McCoy.
"I'm like, 'No, Mike, I don't need you to lead- block!' " Kelly said. "But that's also one of the things that made Mike such a great player, is that he was so competitive that he wanted to win every single snap he was out there. It's kind of a rare combination that Russell has."
The Eagles may have an upper hand in preparing for a zone-read quarterback because they practice so often against it, but defensive coordinator Bill Davis said it's an effective tool because it adds another run-gap responsibility for defenses.
"When the quarterback is a runner and they have a blocker in front of him, or even the zone-read where they're trying to read the commitment to the dive or the quarterback, you just have . . . one more number in the count of the running game and of the gaps available," Davis said.
The Cowboys were cheating toward stopping Darren Sproles and didn't account for Sanchez's gap when he made them pay with a 13-yard scamper in the fourth quarter. Carroll said the threat adds another element that his defense will prepare for on Sunday.
If Sanchez can hold an unblocked defender - typically an edge rusher - as he "rides the running back" and decides whether to hand off or keep, it gives McCoy and Sproles one less tackler to worry about.
"It holds some guys. I'm used to them guys just crashing the reads," McCoy said after the Cowboys game. "They figure [they would] rather live with the quarterback running than let Shady get it. But when he pulls it, it keeps the guys honest, and I can get the ball and run a little bit."
Many of Wilson's rushing yards have come on scrambles, but some of his longest carries have been on zone-reads. He ran for 40 yards two weeks ago against the Cardinals. Two weeks before against the Giants, he picked up 71 yards on seven zone-read runs.
The Giants kept crashing down on running back Marshawn Lynch, and Wilson took advantage.
"I'm trying to hand the ball off 100 percent of the time to Marshawn Lynch," Wilson said. "But if for some reason there's just nobody out there, then I take it."
Foles had some moments in the zone-read. Last season, he scored a touchdown against the Buccaneers and gained valuable yards down the stretch against the Packers. But he has trouble sliding, isn't particularly mobile, and hadn't run as much this season before he broke his collarbone.
It's unclear whether Kelly was calling fewer zone-reads or Foles simply wasn't running. Sanchez isn't a burner, but he could propel his coach to use the zone-read more often. It's only one tool in the toolbox, and further down on Kelly's list of quarterback prerequisites, but it's hard to imagine him not wanting it all, if possible.