Vikings quarterback JJ McCarthy suffers another setback in his underwhelming NFL career

Vikings quarterback JJ McCarthy is in the concussion protocol following Minnesota's loss to the Green Bay Packers.

The 22-year-old has suffered a miserable start to his NFL career and this represents the latest setback for the ex-Michigan star.

Head coach Kevin O'Connell revealed on Monday that McCarthy first reported concussion symptoms on the team's flight home from the 23-6 loss at Green Bay. 

Vikings medical staff made the decision to put the quarterback in the protocol after returning to Minnesota. But O'Connell would not reveal more details about the severity or nature of McCarthy's symptoms. 

The head coach did not rule him out of this Sunday's trip to the Seattle Seahawks but said rookie backup Max Brosmer would step in with the first-string offense in practice this week - until or unless McCarthy is cleared.

'[He] reported some kind of symptoms in regards to his head, and we wanted to get back here once we kind of heard he was evaluated last night,' O'Connell explained.

'After completing those tests, our training staff and doctors and medical team have decided that the right place for him is to put him in the protocol for now.'

O'Connell added: 'I'm not ready to make any sort of designation for the game or anything like that... we'll let the process play out.'

With 10th-year veteran Carson Wentz out for rest of the season following shoulder surgery, the only other quarterback on Minnesota's roster is John Wolford, a 30-year-old journeyman on the practice squad.

McCarthy missed his rookie season recovering from knee surgery and sat out five more games this season with a high ankle sprain.

When he has been on the field, the 22-year-old has struggled mightily to find any kind of rhythm. He went 12 for 19 for 87 yards with two interceptions and five sacks against the Packers, as the Vikings (4-7) lost their third straight game.

According to ESPN's metrics, McCarthy has a QBR (quarterback rating) of 24.8 after six NFL starts, which ranks 33rd (out of 33) this season and among the worst career starts of any quarterback over the past decade.