KNOXVILLE, Tenn. (AP) Tennessee guard Marcus Jackson will undergo potential season-ending surgery, leaving the Volunteers without the most experienced member of an offensive line that allowed the most sacks in the Southeastern Conference last year.
Volunteers coach Butch Jones didn't disclose the nature of Jackson's injury and said there's no set timetable for his recovery but added that ''it could be the season, it could be eight months, it could be nine months.''
''If he has any opportunity of returning, it would probably be toward the tail end of the season (or) to a bowl game,'' Jones said.
Jackson leads all Tennessee offensive linemen with 17 career starts, including 12 last season at left guard after redshirting in 2013. Jones said sophomore guard Jashon Robertson already had asked about the possibility of switching his uniform number from No. 73 to Jackson's No. 75 as a way of honoring his injured teammate.
Jackson's injury hurts Tennessee significantly at an area that already represented perhaps the Volunteers' biggest weakness.
The linemen have spoken throughout the offseason about how their additional experience should help them fare better this fall. Last year, Jackson was the only Tennessee offensive lineman with any career starts. Now he's one of seven linemen with starting experience.
Senior tackle Kyler Kerbyson and Robertson started all 13 games for Tennessee last year. Senior center Mack Crowder made 11 starts, and sophomore tackle/center Coleman Thomas started five games. Sophomore Brett Kendrick and junior Dylan Wiesman made two starts each.
''I like having pressure on us,'' Kerbyson said last week. ''I feel like it makes us better. I really want it to be on us. Everyone talks about the skill guys, (how) they're young but they're talented. It's always a question mark with the o-line, but I want to show people that we're the glue that holds it together.''
Jackson wasn't the only offensive lineman sitting out Tuesday morning's workout. Robertson missed his second straight practice with a sprained ankle, though Jones expects him to return in the next day or two.
Jones said he believed the offensive line ''took a big step forward'' with the way it played Tuesday morning while missing key performers, but he also acknowledged the problems that could arise if injuries force Tennessee to play freshmen.
''It's so different being a youngster in the offensive line and defensive line than any other position group because when you're a defensive back or a wide receiver, you have time to make up for a mistake because you have a 7- to 10-yard radius where you can make up for it,'' Jones said. ''When you play on the interior fronts - the offensive and defensive lines - with one step you're beat.
''You have one second to make a quick decision and then play with pad level and physicality. That's why it's very rare you see true freshmen playing immediately (on the line).''
In other injury news, Jones said cornerback Justin Martin has a knee sprain that could cause him to miss 1 to 1 1/2 weeks. Jones also said defensive back Evan Berry is out about a week without mentioning the nature of his injury.