Oklahoma starting quarterback Jackson Arnold is entering the NCAA transfer portal, sources told ESPN on Wednesday.

Arnold will have two seasons of eligibility remaining at his next school. The 6-foot-1, 210-pound sophomore from Denton, Texas, was the No. 3 recruit in the ESPN 300 for 2023 and started 10 games over his two seasons with the Sooners.

Arnold threw for 1,421 yards on 63% passing with 12 touchdowns and three interceptions in his first season as Oklahoma's starter and also rushed for 444 yards and three more scores.

The preseason No. 16 Sooners went 6-6 in their first year in the SEC while struggling with injuries and inconsistency on offense. Oklahoma coach Brent Venables fired first-year offensive coordinator Seth Littrell after a 4-3 start.

There's expected to be significant Power 4 interest in Arnold when he officially enters the portal Monday, the first day underclassmen can transfer during the winter portal window.

Arnold, a former Gatorade Player of the Year, served as Dillon Gabriel's backup during his first season with the Sooners and was elevated to become their starter for their Alamo Bowl loss to Arizona in December.

Arnold was benched during the second quarter of Oklahoma's 25-15 loss to Tennessee on Sept. 21 after three early turnovers in the program's first SEC conference game. True freshman Michael Hawkins Jr. replaced him to finish the game and started the Sooners' next two conference games against Auburn and Texas.

After Hawkins had three first-quarter turnovers against South Carolina, Arnold again took over as the Sooners' starter and held onto the job for the rest of the season. Following the 35-9 home loss to the Gamecocks, Venables fired Littrell and made co-OC Joe Jon Finley the interim playcaller on offense.

Arnold led the Sooners to a stunning 24-3 upset win over No. 7 Alabama on Nov. 23 to clinch bowl eligibility, rushing for a career-high 131 yards on 25 carries in addition to 68 passing yards on 9-of-11 passing.

The Sooners rank No. 94 nationally in scoring offense this season, averaging 21.2 points per game against FBS opponents, and No. 126 in yards per play (4.8). That production represents a dramatic decline from a 10-win season in 2023.

Oklahoma's projected top five wide receivers -- Deion Burks, Nic Anderson, Jalil Farooq, Jayden Gibson and Andrel Anthony -- missed significant time due to injuries. The Sooners also endured seasonlong struggles and injury setbacks along their offensive line, relying on eight different starting lineup combinations over 12 games. Arnold was sacked 34 times on the year, tied for sixth most among FBS quarterbacks.

Venables hired Washington State offensive coordinator Ben Arbuckle on Monday and is expected to pursue a transfer quarterback addition for next season to replace Arnold.