University of Houston quarterback Case Keenum had an impressive career in college yet failed to get drafted by an NFL team during last week's draft. But Keenum soon found a team after he signed with the Houston Texans yesterday.

It's really unbelievable, Keenum said Monday on the University of Houston campus, the Associated Press reported. I'm extremely excited for so many reasons.

Keenum, 24, shattered many college football passing records while at Houston and is the NCAA's all-time leader in total passing yards, touchdowns and completions.

But Keenum was considered to be a product of Houston's offensive system, which some detractors say bloated Case Keenum's statistics.

Keenum said he'll have a chip on his shoulder after being passed up in last week's NFL draft. Being overlooked has been a theme in Keenum's career, with Houston being the only school to offer the quarterback a scholarship.

 That's just kind of part of my identity, Keenum told the AP. Coming out of high school, I had one scholarship offer. I said that before the draft that all I need is one chance, and I got my one chance here, with a great organization and great coaches.

Texans quarterback T.J. Yates is expected to be the backup to Matt Schaub. Houston is in need of quarterbacks after last year's backup, Matt Leinart, is expected to sign with the Oakland Raiders.

When Schaub went down with an injury last year, Leinart also had injury woes and the Texans had to use third-stringer Yates towards the end of the season and during the Texans' first-ever playoff berth.

Keenum will have to learn a new system with the Texans, which will be much different from the Air Raid-style offense he led at the University of Houston.

Case Keenum's former quarterbacks coach at Houston, Kliff Kingsbury, said he believes Keenum can make the transition to the pros.

Knowing him, I think whatever situation he's put in, he's going to shine and excel and embrace the challenge, Kingsbury, now the offensive coordinator at Texas A&M, told the Houston Chronicle. I'm excited to see him being in a system like that, in which I think he fits well. To be around a coach like coach [Gary] Kubiak, who I know personally how good he is with quarterbacks, I don't think he could be in a better place.

Keenum joins fellow undrafted quarterbacks Kellen Moore [Boise State,] and Aaron Corp [Richmond] as quarterbacks who signed with an NFL team thus far.

Going undrafted does not necessarily mean a quarterback can't be successful. Click through the slideshow to see examples of undrafted quarterbacks who went on to have stellar careers in the NFL.