Irvin started out as a free safety with Mt. San Antonio.
"He came late into camp, but he was a great athlete, so he played and he was on all our special teams," Jastrab said. "The next year, one of our coaches said, 'Hey, can you help us rush the quarterback?'"
Irvin didn't resist, but he didn't like putting his hand in the dirt. He soon realized he was just too fast for offensive tackles, and eventually for double teams, and then he took off by taking passers off their feet.
He had 16 sacks as the Mounties won a national title in 2009 and Irvin was named a junior college all-American.
"Sometimes he killed the quarterback," Jastrab said. "He'd hit the quarterback so hard he'd get a penalty."
Irvin is WVU's first first-round pick since Adam Jones was picked No. 6 overall by the Tennessee Titans in 2005. Tight end Anthony Becht (2000), defensive end Renaldo Turnbull (1990), offensive lineman Brian Jozwiak (1986), fullback Dick Leftridge (1966), linebacker Chuck Howley (1958), fullback Joe Marconi (1956) and offensive lineman Joe Stydahar (1936) are the school's only other first-round picks.
Irvin joined the group despite only two years at the Division I level and hardly what talent scouts would consider extended playing time. On one of the nation's best defenses in 2010, Irvin was No. 2 nationally with 14 sacks, but he played about 225 total snaps and 15 or fewer in five games.
He never thought about entering the draft because, as he said, he didn't want to be a third- or fourth-round draft pick and was instead obsessed with being taken in the first round.
Irvin started just six games last season and dipped to 8 1/2 sacks, but was disruptive enough that opposing offenses had to game-plan for him. Irvin, who was nevertheless first-team All-Big East in 2011, ended his career strong with a key sack and forced fumble at the end of the first half of the Orange Bowl rout.
The 6-foot-3, 245-pound Irvin ran the 40-yard dash in 4.5 seconds at the combine and added a 123-inch broad jump.
"This is a great picture for anyone who's made a mistake and wants to turn their life around," Jastrab said. "I'm proud, almost like a father, to see a kid do what he's done after he was at his wit's end and really not sure what he was going to do with his life."
Carroll recruited Irvin when the defender was in junior college, and Irvin visited USC before choosing to play at WVU.
"I've known the guy for a long time and I know what he brings to a football team and the excitement he generates," Carroll said Thursday night. "He's a great pass rusher. The speed he brings is so unique and so rare. When he had his opportunity to show it in the college game, he came out as the best pass rusher in America.
"This guy is going to be a great asset to the program. I love that we had a background with him all the way through, when maybe other teams didn't. And maybe they didn't have an understanding of what the kid is all about and what he brings. We thought we had special information all the way though."