Clayton Thorson hasn’t been the same quarterback. Through the first five weeks of the season, it’s evident that the ACL injury he suffered in last year’s Music City Bowl is affecting him more than he’d lead you to believe.

That’s not a knock on Thorson, by the way. It’s just an example of the severity of those kind of injuries. Sometimes, that kind of damage sidelines players for more than a year. And there was Thorson, taking snaps against Purdue eight months later.

Pat Fitzgerald and the Northwestern medical staff have kept an eye on Thorson in the early stage of the season, recommending a “pitch count” for the senior quarterback. T.J. Green rotated in through the first three games of the year, as to not overstrain or overwork the newly repaired ACL.

Green came in relief for five possessions in the season opener against Purdue, then five more against Duke. It was three series in the Akron game. And last week, against Michigan, it was zero.

Five weeks into the season, and coming off a bye week, Thorson played the entirety of a game, the first time since the end of the 2017 regular season. He completed 16-of-27 passes for 174 yards and helped propel the Wildcats to a 17-0 lead against the 14th ranked Wolverines.

Northwestern eventually lost 20-17, dropping to 1-3 on the year.

“I was ecstatic to have him there the whole game, he made some big throws, he’d like to have a blocking checkdown back,” Fitzgerald said at his weekly press conference Monday. “He had some throws he would’ve liked to have had back, like he said. But head coaches and quarterbacks are all evaluated on wins and losses, we’ve lost 3 straight and we need to fix that.”

Thorson’s full availability — assuming he’s off that pitch count moving forward — couldn’t come at a better time. The Wildcats are entering the most pivotal stretch on the calendar.

Northwestern’s next three games are all winnable matchups: at No. 20 Michigan State, vs. Nebraska and at Rutgers. But in order to post three wins, and potentially climb back into the B1G race (1-1 in conference), the Wildcats will need the absolute best from their senior quarterback.

It’s not like Thorson has been awful in his first four games. He’s thrown for 927 yards while completing 61 percent of his passes. He’s got as many touchdowns as interceptions, throwing three of each.

Even during a stretch that includes Nebraska (0-4) and Rutgers (1-4), Thorson has to be better. Especially without Jeremy Larkin in the backfield and a rushing attack that ranks dead last in the B1G and 123rd nationally.

Credit: Quinn Harris-USA TODAY Sports

If you believe in owning an opponent, then this critical three-game window couldn’t start with a better opponent. Thorson has dominated Michigan State over the last two seasons. He’s thrown for 637 yards and completed passes at a 72 percent clip. He’s accounted for seven total touchdowns.

And if you believe in historical trends, the Spartans might again be the perfect opponent to help the Wildcats get back on track.

In 2016, Northwestern was off to a 1-3 start before traveling to No. 21 Iowa. Thorson completed 18-of-30 passes for 164 yards. He had three touchdown passes and no interceptions. The Wildcats knocked off the Hawkeyes 38-31 at Kinnick Stadium, sparking a three-game winning streak.

That’s what Northwestern needs from Thorson this weekend. And during this crucial three-game stretch. And for the rest of the season.

Wins in the next three games would give Northwestern serious momentum heading into a much more difficult portion of the schedule. Rattling off three B1G wins puts them right back in the race in the West before games against No. 16 Wisconsin, No. 6 Notre Dame and Iowa.

Northwestern would control its own destiny heading into matchups with the top two teams in the division. Crazy stuff for a team with a 1-3 record.

None of it will matter if Thorson doesn’t deliver.

It’s on the coaching staff and offensive line too, by the way. There has to be some semblance of a rushing attack. Pass protection has to be more effective and recognize that Thorson isn’t as mobile as the past. Wide receivers can’t drop the easy passes. Those have all been issues through the first four games.

Eliminating the rotation under center should help with some of that, and will allow Thorson to get into a better rhythm. But those are all still areas of concern.

If there’s anything we’ve learned from the past, it’s to never count out a Fitzgerald-coached team. After that 1-3 start in 2016, the Wildcats finished 7-6. Last season, they started 2-3 before rattling off eight consecutive victories and ending the year 10-3.

There’s still a chance Northwestern works itself back into the race in the West Division. But that’s contingent on Thorson’s success and whether he can manufacture some of the best football he’s played in his 43-game career.

Thorson’s full availability comes at a perfect time. Now, he has to produce on the field.

If he does that, history might repeat itself in Evanston.