NORMAN, Okla. (AP) — Like a well-executed blitz, Bob Stoops shocked the college football world.

Oklahoma’s football coach abruptly announced his retirement Wednesday after leading the Sooners to 10 conference championships and a national title in 18 seasons.

The 56-year-old Stoops was the longest-tenured active coach in major college football, taking the job at Oklahoma a day before Kirk Ferentz started at Iowa. He went 190-48 (.798 winning percentage) at Oklahoma in his only college head-coaching job, giving him more victories than Sooners greats Barry Switzer (157) and Bud Wilkinson (145).

With his success and the school’s winning tradition came pressure. Many in the restless fan base were frustrated that the Sooners hadn’t won a national title since 2000, even though Stoops’ teams played for three more national titles during his tenure.