The New England Patriots are once again in the Super Bowl. They’re there because of head coach Bill Belichick. They’re there because of quarterback Tom Brady. They’re there because of tight end Rob Gronkowski.

Obviously, there are more reasons behind New England’s trip to Minneapolis, but if you listed all of them by importance, those three probably come out on top in some order. Two of three have few question marks heading into Sunday's big game -- Brady had his hand issue prior to the AFC Championship, but we appear to be past that. For as much as Belichick will mope around during the pregame festivities, there’s no one who will be more prepared come Sunday.

But then there's the big question surrounding Gronkowski. The Patriots tight end suffered a concussion against the Jacksonville Jaguars, and while he has been at practice for the past few days, he has yet to clear concussion protocol. He was even kept away from the media circus of Opening Night, an event he might enjoy even more than the game.

There’s still a better part of a week for Gronkowski to be cleared, but as is the case with concussions, there’s never a concrete timetable. This raises what might be the biggest question to get thrown around either until kickoff or when we find a suitable answer: What happens if Rob Gronkowski doesn’t play?

Major Impact

We all know Gronkowski has a major impact on both how the Patriots scheme on offense and how opposing defenses scheme against them. There’s just no simple solution for covering the guy. There hasn’t been since he came into the league, and no one has come close to finding out a future solution. Very few players have the ability to cover the tight end one-on-one and even in that rare occurrence, he might just win anyway.

Gronk was the most efficient pass catcher in the league this season by our Net Expected Points (NEP) metric. He was football's only high-usage receiver to be worth over an expected point per target, and his 1.03 mark led tight ends by a significant margin. The next best tight end with at least 50 targets was Cameron Brate of the Tampa Bay Buccaneers at 0.83. Only two tight ends with any targets had a higher Reception NEP per target than Gronk, and both of them were thrown at just two times each. The closest wide receiver to Gronkowski was Marvin Jones of the Detroit Lions, who posted 0.98 Reception NEP per target on 107 throws his way.

There have been 10 other players since 2000 that have seen at least 100 targets and posted a 1.00 Reception NEP per target or better — not bad since there’s been 780 100-plus target seasons in that time. It’s been done two other times by a tight end — Antonio Gates in 2009 and Rob Gronkowski in 2011.

Everything about Gronkowski was as advertised this past season. When he was on the field, he was one of the league's most dominant forces. He also missed a few games, which is wonderfully convenient for what we’re trying to figure out here.

Two Tom Bradys

Unsurprisingly, the player impacted the most by whether Gronkowski is on the field or not is Tom Brady. He led all quarterbacks with at least 200 drop backs in Passing NEP per drop back this season, and while Brady had another great season, he performed much differently with Gronkowski in and out of the lineup. The two games Gronk missed also featured the two lowest point totals of the season for New England — 19 points in a win against the Buccaneers in Week 5 and 20 points in a Week 14 loss to the Miami Dolphins. It’s not hard to see why.

Below are Brady’s per-game averages with and without Gronkowski in the lineup (thanks to the Rotoviz Splits tool).

Two games is a small sample, but Brady’s drop in performance follows a larger pattern. Since 2011, the year Gronkowski really became Gronk, Brady has about a season and a half worth of games without the massive tight end. The splits are similar to what we saw in 2017.

Without Gronkowski, Brady has put up a yards per attempt number similar to the 2017 versions of Dak Prescott and Derek Carr. That’s not what you’re hoping for when one of the greatest quarterbacks ever steps on the field.

Other Adjustments

Brady isn’t the only player who be impacted by a Gronkowski absence. For those other players, though, they’re likely to see a boost in performance — or at least that's what the Patriots hope.

Let’s look at three of the other big pieces of the New England offense — Brandin Cooks, Danny Amendola, and Dion Lewis — and how they played with Gronk on and off the field this season. First, here’s how each fared in the games with Gronkowski:

And here’s how roles and production changed without him.

Volume goes up for all three, but Cooks did not see his production increase — his receptions went down while his yards stayed about the same. It was Amendola and Lewis who become bigger parts of the offense.

Amendola had 8 receptions on 8 targets for 77 yards in Week 5 against the Buccaneers without Gronkowski and tied a season-high with 9 targets against the Miami Dolphins in Week 14. In that Miami game, Lewis had 5 receptions on 5 targets for 50 yards. The yards were a season high, while the targets and receptions were only topped in the Week 17 matchup with the New York Jets, a game Gronkowski played, but was not targeted.

Losing Gronk wouldn’t immediately mean the Patriots will run the ball more. Against Miami, New England ran the ball 10 times for a total of 25 yards. The Dolphins were much better defending the run (12th by Adjusted Defensive Rushing NEP per play) than the pass (24th by Adjusted Defensive Passing NEP per play) so the Patriots decided to attack them through the air.

There’s not as big of a gap for the Eagles defense, a unit that was good at everything — third by Adjusted Defensive Rushing NEP per play and fourth by Adjusted Defensive Passing NEP per play. New England, on the other hand, was much better throwing the ball on offense (first by Adjusted Passing NEP per play), but was still efficient on the ground (eighth by Adjusted Rushing NEP per play).

Still, it may be hard enough for the Patriots to move the ball on the Eagles with Gronkowski in the lineup, nevermind without their best offensive skill player. It seems unlikely that New England will have to figure it out, but until Gronkowski’s return is official, it’s possible the best adjustment coach in the league will have to make a massive one before Sunday.