Quincy Enunwa’s season has been ended by a serious neck injury for the second time in three years.

The Jets wide receiver was placed on injured reserve Tuesday, after the team learned Monday that his injury was severe. That’s a scary situation for Enunwa, who sustained his first neck injury in 2017 training camp and missed the entire season. This time, he played one game.

Coach Adam Gase wasn’t sure whether this injury is related to the last one — or if it could threaten Enunwa’s career. Enunwa is still seeking more tests and medical opinions. But from the outside looking in, there’s at least some chance this could be the end of the line for him. The question is how big a chance.

If Enunwa’s career is indeed finished, how would that impact his cash flow and the Jets’ salary cap in the future? After all, this is his first season of a four-year, $36 million contract extension.

There are a few scenarios going forward, but one is far more likely than the others. Before we get there, here’s a refresher on Enunwa’s contract details:

Signing bonus: $9 million (spread for salary cap purposes over five years because Enunwa signed his contract before the end of the 2018 season, so the cap hit is $1.8 million per year)

Fully guaranteed money at signing: $10 million (signing bonus plus 2019 salary)

Effective guaranteed money at signing: $16 million (signing bonus plus 2019 and 2020 salaries)

2019: $1 million salary (guaranteed), $2.8 million salary cap figure

(Enunwa’s 2019 salary became fully guaranteed on the fifth day of the league year in March.)

2020: $6 million salary (guaranteed), $7.8 million salary cap figure, $5.4 million dead money figure

(Enunwa’s 2020 salary becomes fully guaranteed if he is on the roster on the fifth day of the 2020 league year. It is currently guaranteed only against injury.)

2021: $7.8 million salary, $9.6 million salary cap figure, $3.6 million dead money figure

(If Enunwa is on the Jets’ roster on the fifth day of the 2021 league year, $4,078,588 of his salary becomes fully guaranteed. It is currently guaranteed only against injury.)

2022: $9.6 million salary, $11.4 million salary cap figure, $1.8 million dead money figure

Injury guarantees are safeguards that allow players to collect their future salaries (or at least part of them) in the event that they sustain a career-ending injury.

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Now, with those details laid out, here’s a look at how this injury could impact the Jets’ future salary cap situation, based on NJ Advance Media’s conversations with NFL salary cap experts, including Jason Fitzgerald from OverTheCap.com:

If Enunwa retires ...

The contract is terminated in the same way as if Enunwa was cut. The Jets get off the hook for all the money that wasn’t fully guaranteed at signing. Enunwa would get $10 million (the signing bonus, plus his 2019 salary), but nothing else. For cap purposes, Enunwa’s signing bonus would all accelerate up and hit the Jets when he retired. So if he retired now, the Jets would eat an $8.2 million cap hit for 2019 (his current $2.8 million cap figure plus his $5.4 million prorated signing bonus). But Enunwa would come off the books next season.

If the Jets cut Enunwa ...

Frankly, retiring would be a horrible financial decision for Enunwa, even if he’s physically unable to play. Why give up all the money guaranteed against injury if you don’t have to? But even if Enunwa doesn’t retire, the Jets can still cut him, to clear future cap hits off the books. But they’d pay a steep financial penalty for it.

If the Jets released Enunwa now, they’d have to pay him all of that future, injury-guaranteed salary immediately. As a result, all of that money would also hit the Jets’ 2019 cap. That’d be about a $10.1 million charge. Plus, they’d have to accelerate his prorated signing bonus ($1.8 million per year) from 2020-22 and apply it all to the 2019 cap. So that’s an extra $5.4 million.

All told, Enunwa’s cap hit for 2019 – if he cannot play and the Jets cut him – would be $18.3 million. Why? Because you have to add his 2019 cap hit ($2.8 million) to the aforementioned $10.1 million (injury-guaranteed future salary) and $5.4 million (prorated signing bonus).

If Enunwa can’t play, but doesn’t retire ...

We already mentioned that retiring would be a bad move for Enunwa. And you just saw the massive up-front financial penalty the Jets would pay for cutting him now. So both of those options are unlikely.

Odds are, Enunwa will hang on and make the Jets keep carrying him on the injured reserve or physically unable to perform list, in order to get his money.

In that case, the Jets have two options: They can do nothing (and spread the cap hits out over the life of his deal) or try to find an optimal time to cut him.

If the Jets just let things play out, they’d have to keep paying Enunwa through 2021, when his injury guarantees run out. And the cap hits would run through 2022, thanks to that prorated signing bonus.

In that case, the salary cap hits would look like this:

2019: $2.8 million ($1.8 million prorated signing bonus, plus $1 million guaranteed salary)

2020: $7.8 million ($1.8 million prorated signing bonus, plus $6 million injury-guaranteed salary)

2021: $5.878 million ($1.8 million prorated signing bonus, plus $4.078 million injury-guaranteed partial salary)

2022: $1.8 million (prorated signing bonus)

That’s a viable option for the Jets. But the more likely scenario is that the Jets keep him on the books for a while, then cut him when it’s most convenient.

Here’s how that would work:

The Jets can dodge a steep single-year payout and avoid Enunwa’s cap hit reaching double digits if they keep him through 2020, then cut him after that. In that case, the 2019 and 2020 numbers would look the same as above – but the rest of the money would all lump together in 2021, clearing Enunwa off the books one year sooner.

The cap numbers would look like this:

2019: $2.8 million ($1.8 million prorated signing bonus, plus $1 million guaranteed salary)

2020: $7.8 million ($1.8 million prorated signing bonus, plus $6 million injury-guaranteed salary)

2021: $7.678 million ($3.6 million in remaining signing bonus money, plus $4.078 million injury-guaranteed partial salary)

If Enunwa gets healthy again ...

Financially speaking, this is the absolute best case scenario from the Jets’ perspective.

If this injury sours the Jets on Enunwa, but he gets healthy by next March, then the team would catch a huge break. Suddenly, the injury guarantees wouldn’t matter anymore, because Enunwa would be capable of playing in 2020. And his 2020 salary doesn’t become fully guaranteed until the fifth day of the 2020 league year (March 22).

So, in between Enunwa passing a physical and that date, the Jets could cut him and would not be on the hook for any of his salaries moving forward. They would, however, accelerate all of his signing bonus money onto the 2020 salary cap. So, they’d eat $5.4 million in dead money, but Enunwa would come off the books for the 2021 season.

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Again, it’s too early to say for sure whether these scenarios will come into play for the Jets. We don’t yet know if Enunwa’s injury is career threatening or not.

But, if it is, the Jets’ decision (under former GM Mike Maccagnan) to give Enunwa a whole bunch of injury-guaranteed money – and keep those guarantees in place all the way through the third year of the contract – could backfire and cost them.

Matt Stypulkoski may be reached at mstypulkoski@njadvancemedia.com. Follow him on Twitter @M_Stypulkoski. Find NJ.com Jets on Facebook.