Oklahoma co-offensive coordinator and quarterbacks coach Josh Heupel has been let go, according to a source.

A formal announcement is expected by Sooners coach Bob Stoops during a press conference later Tuesday morning. The move marks the end of one of the most successful offensive periods for the Sooners.

The 36-year-old has been Oklahoma's play-caller since 2011 when he was promoted from quarterbacks coach.

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The Sooners ranked in the FBS’ top 20 in scoring offense in three of Heupel’s four seasons, including 20th this season at 36.4 points per game. That’s despite Oklahoma’s total defense slipping to well outside of the top 20 nationally over three of the prior four seasons.

Heupel has been one of college football’s best offensive play-callers the last four years. Entering the Sooners’ regular-season finale this year, he was fourth over the last four years in points per game (37.4) behind only former Baylor offensive coordinator and new Tulsa head coach Philip Montgomery, Texas Tech coach Kliff Kingsbury and Florida State coach Jimbo Fisher.

Prior to Oklahoma, Heupel was the tight ends coach at Arizona for a season and a graduate assistant for the Sooners from 2003-04. The Aberdeen, S.D. native was also a beloved quarterback for Oklahoma who on the field led Stoops to his only national championship in 2000. Heupel was the runner-up for the Heisman Trophy that season.

Earlier this week, Oklahoma's other co-offensive coordinator, Jay Norvell, was also let go.