Johnny Manziel has seen his share of critics say he doesn't have what it takes to succeed as an NFL quarterback.

Whether it be his height (a listed 5-11-3/4 at the combine) or the notion that he leaves the pocket too soon, the former Heisman Trophy winner has heard it all.

Speaking at the NFL combine on Friday, Manziel said he's looking to prove those people wrong.

"I'm just looking to show up all the people who are saying that I'm just an improviser, I feel like I worked extremely hard this year to all around hone in on my game," Manziel said. "So continuing to do that. I'm working out in San Diego, continuing to do that and get better as a pocket passer and a quarterback in general."

Asked about his height, Manziel said, "I feel like I play 10 feet tall." It's clear there's a level of confidence to Manziel the NFL will soon see.

And that confidence translate into a high level of competitive nature.

"I think I'm probably one of the most competitive people on the face of the earth," Manziel said. "Whether it's sitting here playing tic-tac-toe or rock-paper-sciccors or whatever it may be, I want to win."

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Aaron Wilson covers the Ravens for The Baltimore Sun.