San Francisco 49ers defensive end Arik Armstead has outlined his desire to hit back at his critics in his rookie season in the NFL.

The 21-year-old was maligned for his displays for the Oregon Ducks during the scouting process ahead of the 2015 Draft as some pundits believed that his performances lacked effort and consistency.

However, the 49ers saw enough talent to select Armstead with the 17th overall pick in the Draft as a long-term replacement for the retired Justin Smith.

"Football-wise, it comes from people not noticing the little things," Armstead told the San Francisco Chronicle. "Me getting double-teamed or triple-teamed on certain plays. But those things help my team win games.

"I'll sacrifice stats and things like that if I'm doing what my coaches want me to do. And if we're winning doing that, I'm happy about it. I'll deal with critics for that. It's fuel to the fire. It's a little extra motivation. Everyone wants to prove people wrong, but it's not my main driving factor. If people say good things about me, I try to prove them right.

"If they say bad things about me, I try to prove them wrong. For me, it's the people who don't have the knowledge about what I'm doing that can be a little frustrating. But it's OK. Everyone has an opinion. I've learned you can't control everyone's opinion."

Armstead recorded 87 tackles and 4.5 sacks in his three years in the college game.