Offensive guard Bartley Miller had shoulder surgery last week and is out for the rest of the spring. Tackle Dennis Roland (bruised leg) was back in uniform Tuesday but was limited to jogging around the practice field.
Guard Josh Brock also was held out as he continues to recover from a sprained ankle.
Of the eight scholarship offensive linemen entering spring practice, only four were left after Tanner's exit Tuesday. The problem is magnified because Georgia has to replace every starter from its 2002 line and, as Callaway said Tuesday, "It's hard for them to learn when they're not here.''
Roland, Tanner and Brock could return as early as Thursday's practice. Miller is expected to be fine for preseason practice, when incoming freshmen will add more depth to the unit.
The problem affects more than just the offensive line. Coach Mark Richt says he can't get a true read on the progress of his defensive line. It also affects his ability to judge the work of running backs and other positions.
"It's a big problem,'' Callaway said. "We're missing four and that's what we're dealing with.''
On Tuesday, walk-on Ryan Schnetzcr of Newnan was with the first-team offensive line at guard. Another new name on the first-team line was Reggie Weeks, the former defensive lineman from Smiths, Ala., who has made a full recovery from a dislocated left knee in 2001.
With such a patchwork effort required to find a first-team line, Richt shakes his head when talking about the difficulty of fielding a backup line.
"It's frustrating that we can hardly get a second line together,'' Richt said. "It's making it difficult for everybody to see what we can do on both sides of the ball. ... There's just not a whole lot of resistance (for the defense).''
The imbalance was so obvious that defensive end David Pollack was held out of a March 13 scrimmage in Sanford Stadium - the team's last practice before spring break - because coaches realized he could not be blocked.
The hope is that Brock, Roland and Tanner will be back by the April 5 G-Day spring game.
"I want to be back as quick as possible,'' Roland said.
Roland was leg-whipped early in one of the first spring practices. Pain in his lower right leg was so persistent that he has been X-rayed twice, but each time the results were negative.
Roland and Inman are expected to compete for a starting job at one tackle spot. Jean-Gilles is the other tackle. Brock is expected to start at one guard spot. Swoopes is pushing Tanner at center, and Weeks is competing with Miller at the other guard spot.
"If we were all there, I'd feel pretty good,'' Callaway said.
Georgia will practice Thursday and Saturday this week, leaving four days to complete the spring schedule next week.
NOTES: Tailback Tony Milton (ribs) was back in uniform Tuesday. "Tony looked good,'' Richt said. ... Kicker Billy Bennett, returning from mononucleosis, was in uniform, though he wore a green jersey for no contact. ... Richt plans a scrimmage for Thursday.