The referees made a key mistake in Arizona football’s upset victory over then No. 10 Utah on Saturday night. They missed a targeting call—a play that cost Arizona quarterback Anu Solomon.

Solomon attempted to slide feet-first to avoid being tackled with just over nine minutes remaining in the game. Instead, Utah’s Jason Fanaika hit a defenseless Solomon and appeared to lead with his helmet.

“We have pictures of it,” Arizona head coach Rich Rodriguez said. “I think the league is going to review it.”

Solomon left the game due to another suspected concussion. The injury poses a possible end to the starting quarterback’s season, although he is currently day-to-day, according to Rodriguez.

According to Rule 9-1-3 of the American Football Coaches Association, “No player shall target and initiate contact against an opponent with the crown (top) of his helmet. When in question, it is a foul.”

A foul is right.

Arizona fans went ballistic and loud boos were heard throughout the stadium as the play was shown repeatedly on the screen.

The play clock for the next play began to tick down and Arizona was forced to call a timeout so trainers could help Solomon off the field.

Rodriguez said Solomon was sitting on the field and didn’t respond to him. As Solomon exited the game, Fanaika didn’t. In fact, he would finish with five total tackles, tied for third in the game among Utah players.

Arizona officials have since filed a formal complaint with the Pac-12 Conference following the incident.

“From where I was sitting from, it looked like it could have been helmet to helmet,” Rodriguez said. “The pictures show that it could have been a possible target. We are going to send it to the league. I don’t know what they will do about it right now, but they will at least talk to the officials about it whether they agree with us or not.”

Longtime Arizona Daily Star columnist Greg Hansen chimed in on Twitter with his thoughts on the hit.

Not trying to over-react, but that illegal hit to Anu’s head could end his career. It’s a violent game https://t.co/wlPxGQ9tLZ

— Greg Hansen (@ghansen711) November 15, 2015

A violent game for sure. Will it end his career? Probably not. But concussions have been a topic of discussion everywhere in the media.

Will Smith’s film “Concussion,” for instance, will release Christmas day this year. The film is about concussions and chronic traumatic encephalopathy.

Solomon may not play against rival ASU in the Territorial Cup on Saturday, which will be Arizona’s final game of the regular season. One side has reportedly taken this too far, however.

Patrick Kinahan from The Zone Sports Network reported on Twitter that one player recently received hate mail.

Utah DL Jason Fanaika says he has received hate mail from Arizona fans for his hit on Anu Solomon that knocked him out of the game

— Patrick Kinahan (@PKKinahan) November 17, 2015

That, my friends, is taking it too far.

UCLA defender Jacob Tuioti-Mariner nearly made a similar play on Washington State’s quarterback Luke Falk on the same night Solomon went down. Falk was immediately taken to the sidelines and wasn’t given his helmet for the rest of the first half.

Fans at the game called for a targeting hit, but the Pac-12 referees did not call one.

Targeting became a rule in 2008 in order to improve player safety, according to the Associated Press.

Two in one night in one conference says a lot—maybe a little bit too much. I thought we were trying to improve player safety, not hurt it.

Follow Matt Wall on Twitter.