A returning starter on Tennessee's offensive line has left the program.

Nathan Niehaus, who started six games at right guard for the Vols in 2018, has elected to leave Tennessee, head coach Jeremy Pruitt announced following Wednesday's practice.

The redshirt junior had participated in each of the first four practices to open the preseason, but he was absent on Wednesday as Tennessee practiced in full pads for the first time.

Pruiit said Niehaus "has left the team" and said it was the player's decision.

Niehaus didn't play in his first two seasons with the Vols, but emerged as a starter up front last season, making his first career start when the Vols upset Auburn last season.

A former standout at Colerain High School in Cincinnati, Niehaus was rated a three-star prospect and ranked the No. 1,060 overall player, No. 90 offensive tackle and No. 47 player in the state of Ohio in the 247Sports Composite for the 2016 class when he signed with Tennessee, then coached by Butch Jones.

He redshirted in 2016 and didn't play in 2017 due to injuries.

Niehaus, who was listed at 6-foot-6 and 285 pounds as a redshirt freshman and worked his way to the 300-pound mark in the year following Pruitt's hire and Craig Fitzgerald taking over the strength-and-conditioning program, impressed Tennessee's current coaching staff with his toughness and versatility and eventually earned his way into the starting lineup by the middle of the season after making a cameo debut at left tackle in the season opener against West Virginia, when he relieved Trey Smith briefly during the first half as the starter had his ankle re-taped.

After making his first career start at Auburn, Niehaus stuck in the starting lineup at right guard for the games against Alabama, South Carolina, Charlotte, Kentucky and Missouri before sitting out the season finale against Vanderbilt due to injury.

He was expected to compete for a starting job on Tennessee's offensive line this season. He spent time at both tackle spots back in the spring. To open preseason practice he was at right tackle, alongside first-teamer Marcus Tatum and five-star freshman Darnell Wright, for the first three practices before working at right guard early in practice on Tuesday.

The Vols still should have plenty of options across the offensive line. Tennessee has five-star freshman Wanya Morris and returning 11-game starter Jahmir Johnson as options at left tackle with Tatum and Wright likely to battle for the right tackle spot. Ryan Johnson, Jerome Carvin and Riley Locklear are capable of providing depth at right guard, where K'Rojhn Calbert has emerged as a likely starter.

Despite a rash of offseason attrition on the offensive line, the position group still has 13 scholarship players following Niehaus's departure.