INDIANAPOLIS -- Detroit Lions general manager Bob Quinn said he was disappointed former Oklahoma running back Joe Mixon was not invited to the NFL combine because he would have liked for all of the teams to be able to evaluate him.

Quinn also told reporters Wednesday that the Lions haven't taken Mixon off their draft board, but admitted it would be "a long conversation" before the team would draft him.

Mixon was one of a handful of players not invited to the combine because of off-field issues. Mixon apologized again last month after surveillance video was released of him punching a female Oklahoma student in the face in 2014. He was suspended for the 2014 season after the assault occurred that summer, but outrage ensued in December when Mixon's attorneys released the video.

"We're going to leave the door open on Joe. I think it's really disappointing that Joe's not here," Quinn said. "We come here to see the best college football players in college football. So there's 330, 340-some odd players here. Him not being here, because of those issues, personally I don't think that's real fair because we have a lot of investigation that we want to do on him and to get him in one spot for all the teams would have been great.

"I'm not part of those decisions about how guys are chosen but I think it is a disappointment that guys like him, there's a few others you can put in that category, that we're going to be chasing around the month of March and April and it's really unfair to the players to be honest with you. So the door is open and I'd like to be able to get a chance to sit down with the people that know Joe or Joe and see what the circumstances were around the incident."

When asked if he thought it was fair that he wasn't at the combine, Mixon shrugged it off.

"Nah, not at all. It's not in my hands, to make that decision," Mixon told TheMMQB.com. "At the end of the day, I respect the NFL not inviting me. And I've got another opportunity to show what I can do, at the pro day. ... They came up with a decision. And like I said, I respect it."

Mixon said that while he won't be at the combine, he'll be watching.

"I'm definitely going to watch the combine. I want to see my [Oklahoma] teammates do their thing," he told TheMMQB.com. "... And then I want to see the competition, obviously, all the running backs I'll be competing against."

Quinn said Mixon is still on Detroit's draft board but that it would be "a long conversation" before he felt comfortable about drafting the 6-foot-1, 227-pounder. He also said if the Lions were to decide they wanted to draft Mixon, it is "absolutely, yes," a decision he would run by team owner Martha Ford.

Mixon was shown on the surveillance video punching Amelia Molitor in the face, breaking her jaw, eye socket and cheekbone after she shoved Mixon and slapped him. Mixon had said in an interview with police that Molitor's friend had said racial slurs and that is what began the entire incident.

The 20-year-old Mixon apologized for the incident in December.

"Some of that stuff that's out on him, it's pretty ... it's out there," Quinn said. "Everyone can look at the video and [see] exactly what happened. What we really don't know is what were the circumstances around that. Like I said up there, this is a long process and I really wish he was here so we could sit down with him and, like, get to the bottom of it."

Mixon told TheMMQB.com that he has learned from his mistake.

"It was a one-time thing. I made a bad decision, I made a bad mistake," Mixon said. "If I could take it back, I would. I can't. So I have to keep moving forward, doing the right things. I can't keep worrying about something that happened three years ago."

Ford was given the Zero Tolerance Award in June 2016 by the Women in Blue of the Detroit Public Safety Foundation for her team's stance toward domestic violence. At his first news conference as the team's general manager, Quinn said he had zero tolerance for domestic violence and gun issues.

He then softened his stance after Detroit signed Orson Charles and Andrew Quarless -- two players with gun issues in their pasts -- last season.

ESPN's Jake Trotter contributed to this report.