The 6-foot-3, 261-pound Mercilus is an early-entry junior who only started for one season in college, but he led the nation in sacks (16) and forced fumbles (8). He earned All-Big Ten honors and won the 2011 Ted Hendricks award.
"He's a smart player, he's athletic, he's tough," Texans defensive coordinator Wade Phillips said. "You want those high-motor guys, but you want them to have that kind of ability."
Phillips said if Mercilus would've stayed in school, he would've been a top-10 pick in next year's draft. Mercilus says he's ready to contribute immediately, despite his relatively light experience.
"I answer that criticism as I just became more of a student of the game," Mercilus said. "Definitely, when I got my opportunity, I made the most of it. Instead of being behind a starter, who was ahead of me in my last years, 2009 and 2010, once I got my opportunity, I was able to make the most of it and just shine through."
Mercilus only started one season at Illinois, but Phillips said his lack of experience didn't deter the Texans.
"They say `one-year wonder,"' Phillips said. "You wonder why he didn't play, is what I wonder. The guy went out and played against the Big Ten and I'm sure they did the right thing. He was ready this year, you see all the athletic ability you look for in a player, especially with his pass-rush skills."
Houston took some key losses in free agency, with career sacks leader Mario Williams, right tackle Eric Winston and right guard Mike Brisiel signing with other teams. The Texans cut Winston and traded All-Pro linebacker DeMeco Ryans to Philadelphia.
Houston opted for another defensive addition, even though Houston coach Gary Kubiak and general manager Rick Smith both said they were eyeing the deep pool of receivers in the draft. Five-time Pro Bowler Andre Johnson, who turns 31 in July, missed nine full games with hamstring injuries last year and the Texans never found a consistent replacement.
The Texans finished 10-6 last season and won their first AFC South title to earn the franchise's first playoff berth. A year ago, Houston used six of its eight picks in 2011 on defensive players, and the first two -- defensive end J.J. Watt and outside linebacker Brooks Reed -- played well in starting roles. The Texans' defense ranked second last season and made the biggest one-year improvement of any team since 1970, allowing about 91 yards fewer per game than it did in 2010.
Mercilus played defensive end in a 4-3 defensive scheme for the Illini, who ranked seventh in total defense last season (286.2 yards per game). Phillips said Mercilus projects to an outside linebacker in the 3-4 alignment that Houston now employs.
"He's a really strong pass rusher," Phillips said. "He fits in really well."
Mercilus says he doesn't know much about Phillips, but he got a good vibe when he met with the team at the combine. He acknowledged that he needs to improve his run defense, but he's confident in transferring his pass-rushing game to the next level.
"I'm nasty, I get after the passer, I'm not going to give up, I'm going to give 110 percent all day, every day," he said. "I'm looking to learn, looking to earn my way through the Houston defense and just try to contribute right away."
The Texans have now taken 13 defensive players with their last 15 picks in the first and second rounds. One exception was left tackle Duane Brown, Houston's first-round pick in 2008, also the 26th overall selection.
The loss of Ryans and Williams created a need for pass rushers and linebackers. Smith said this week that he likes the depth of linebackers in the draft, and defensive coordinator Wade Phillips says Mercilus was the best player on the Texans' board when their pick came up.
Phillips says Mercilus is ahead of where Reed was when Houston drafted him last year. Reed registered a sack in five consecutive games, the longest streak in team history.
Kubiak has a pattern of moving top draft picks quickly into the lineup. Since he became Houston's coach in 2006, first-round picks have started all but two games in their rookie seasons. Brown, linebacker Brian Cushing (2009), cornerback Kareem Jackson (2010) and Watt all started 16 games as rookies.
All but three of Houston's 25 draft picks since 2009 are still on the roster.
The Texans had eight picks overall. They'll have No. 26 in the second round and No. 13 in the third round.