Detroit Lions corner Terrion Arnold learned a lot in his rookie debut. There was a mix of both positive plays and errors in judgment, but his confidence never wavered, and he walked away from the season opener with the respect of the superstar he was tasked with guarding most of the night: former Offensive Player of the Year, Los Angeles Rams wide receiver Cooper Kupp.

“As a cornerback, you have the toughest task. Just go out there and (see for yourself),” Arnold said in the locker room after the Lions’ overtime victory over the Rams. “Cooper Kupp is a great player. So, me guarding him—even after the game, (I went) up to him and he was like, ‘Yeah, you one of those ones.’ It was a great game, great matchup going against him, and liked it.”

That’s a heck of a compliment from Kupp, who had a stellar day as Matthew Stafford’s primary target. While Arnold was not responsible for ceding all of Kupp’s production, the pair faced off quite a bit, and the veteran receiver came away impressed.

“I mean, he’s a competitive football player, I think that’s the thing,” Kupp told MLive’s Kory Woods after the game, via Ben Raven. “As a young guy, being able to come up and compete and challenge guys. He’s just going to continue to get better, I know, as the year goes on. You see those guys talking, the safeties, they’re communicating with him and trusting him. I think that’s something that’s going to be cool for him just to grow this year. It’ll be fun to watch him from afar. But it was certainly fun competing against him.”

Arnold was a bit more critical of his performance, citing two pass interference penalties that occurred when covering receivers on corner routes.

“I felt like I played alright,” Arnold said. “Normally, on those corner balls—like that (last) corner ball, I was mad at myself because I feel like I could have turned and made a play. And that would have been a big momentum shift. But (in that regard), just having a short-term mentality, those PIs (pass interference penalties)—I hold myself to a high standard, so I felt like those kinda hurt our team. But I take full accountability for it. I’m gonna get back to the drawing board and get better.”

While going back and looking at the game film will give him a better perspective on where things went wrong, in the immediate, he felt improvements will start with hand placement and getting his head around to locate the football.

“I feel like I could have been better with my hands (and) looking back for the ball,” Arnold continued. “And those are plays I have to look up, take the risk of looking at the ball, and make those plays.”

Arnold felt his mistakes were correctable and Lions coach Dan Campbell appeared to agree, based on his post-game press conference comments.

“When I saw just the replay of both of them, I wasn’t too concerned,” Campbell said. “I know why they threw them, especially the second one, like ‘OK, I got it, I understand.’ It’s ticky-tacky but that’s what they do. They’re going to throw it because they believe it, they see it, and all good. We overcome it. But no, I didn’t feel like it was some blatant, like, ‘Oh, he’s out of bad position, or I need to talk to him about it.’ I don’t want to take away his stinger. I want him to play aggressive, and I thought he did some really good things today. Certainly was not too big for him.”

The Lions’ came away content with the production they got out of their rookie, and believe his mistakes are correctable. This was certainly a tall task for Arnold’s NFL debut, and at the end of the day, the rookie remains as confident in himself as ever.

“I know I am ‘one of them ones,’” Arnold reflected back on Kupp’s compliment. “I mean I know I am a great player. I go out there and play with confidence and it’s a testament to my hard work.”