The Jets were dealt a major injury blow just one week into the season.

Starting wide receiver Quincy Enunwa suffered a neck injury in Sunday’s season-opening loss to the Bills and will not be able to return this year. This is the second serious neck injury Enunwa has suffered. He missed the entire 2017 season after injuring his neck in training camp that year. It is unclear whether this injury is considered career-threatening.

Jets coach Adam Gase confirmed the news, which was first reported by The Post.

“You lose a starter. You lose a guy that is a veteran player that has been through a lot and that’s done a lot of good things,” Gase said. “He’s done everything you possibly could ask a guy to do. He tries to do everything right. He works hard. He studies. He tries to lead by example. He speaks up when he has to. The way he plays, everything is violent and he gives everything he has. I feel for him just in the aspect that he’s going through something like this.”

Enunwa left Sunday’s game in the first quarter briefly and then returned. He only had one catch for [minus]-4 yards in the game and was targeted just three times.

Gase said Enunwa informed them Monday that he still did not feel right and was sent for tests. Those tests showed the seriousness of the injury and the doctors ruled him out for the season. Gase said Enunwa was seeing a specialist and undergoing more tests. He was not sure if this could end Enunwa’s career.

“I don’t want to say that because I’m not a doctor,” Gase said. “I don’t understand the details of everything.”

The trade for Demaryius Thomas on Tuesday now makes more sense. The Jets sent a 2021 sixth-round pick to the Patriots for the 31-year-old veteran receiver. It was initially thought to be just a move to add some depth to a thin position group. Now, it is clear the Jets were trying to find someone to replace Enunwa in the lineup.

Thomas did not practice Wednesday. He watched in street clothes, but Gase sounds hopeful Thomas can play Monday against the Browns. Thomas, 31, spent much of his time with the Patriots recovering from a torn Achilles tendon he suffered in December while with the Texans. He played in the final preseason game and scored two touchdowns against the Giants.

“He looked good in that last preseason game that we watched,” Gase said. “He seems like he’s in a good place. We’ll just see how it goes. He knows the offense. He can easily be plugged in. He still remembers everything.”

Enunwa, 27, signed a four-year, $36 million contract extension in December that included a $9 million signing bonus and a guaranteed $1 million salary for this season. His $6 million salary for 2020 was guaranteed for injury.

The 2014 sixth-round pick has had trouble staying healthy throughout his career. He missed five games last season with ankle injuries. He caught 38 passes for 449 yards and one touchdown in 2018.

Enunwa’s best year came in 2016 when he had 58 receptions for 857 yards and four touchdowns. He then injured his neck during a practice at MetLife Stadium in the 2017 preseason and missed that entire year.

Enunwa has 119 career receptions for 1,617 yards and five touchdowns.

The Jets will miss Enunwa’s versatility and his ability to gain yards after the catch. At 6-foot-2, 225 pounds, Enunwa is built more like a tight end and Jets coaches have moved him around through the years.

Gase had spoken highly of Enunwa this offseason and seemed enthusiastic about Enunwa’s potential in his offense. That won’t happen this year now.

“It sucks,” running back Le’Veon Bell said. “Obviously, you don’t want to see a guy like Quincy go down. I’m praying for the best for him. Obviously, that’s a scary injury. I didn’t know he got hurt. That’s how tough he is. He’s playing the game. I guess he was injured. I didn’t even know. He didn’t tell nobody. You don’t want to see a guy go down like that, but we’ve got to plug guys in and we’ve got to keep rolling.”

Without Enunwa, the Jets’ receiving corps looks like this: Thomas, Robby Anderson, Jamison Crowder, Josh Bellamy and Braxton Berrios. The Jets also can use running backs Le’Veon Bell and Ty Montgomery as receivers because of their pass-catching ability.

The Jets offense is already missing tight end Chris Herndon, who is serving a four-game suspension to start the season. Losing Enunwa is another tough blow for the unit.