Tubbs was originally diagnosed with sprained left ankle, but sources said X-rays Tuesday night revealed a broken bone. An official announcement is expected today.
Teammates already feared the injury may have been worse than a sprain after Tuesday's practice.
"He's tough guy, so I'm sure if it was something minor, he would have gotten up," said left guard Stephen Parker. "If it's not broken, I'm sure he'll fight through it and be ready for Auburn (the Hogs next game on Oct. 16)."
The injury occurred on a running play during middle drill and freshman fullback Farod Jackson said he saw what happened.
"It didn't look too good," Jackson said. "Another lineman rolled up on his foot when it was planted and somebody came in and hit him from another direction, so it got twisted the wrong way.
"It looked like it really hurt, especially from the noises he was making."
Tubbs, a 6-foot-6, 351-pound junior from Cullman, Ala., has started all five games this season and has made seven career starts.
"He was always grading out real high and he was our best lineman (in Saturday's 45-30 loss at Florida)," Parker said. "We run a lot to the right side behind him and his pass blocking has really improved. He's been real solid for us and we're praying he's OK."
In his place, Arkansas used redshirt freshmen Nate Garner (6-6, 312) and Matt Gilbow (6-6, 300) for the remainder of practice.
The key for the reserves will be gelling with the first team should Tubbs not return.
"They've got to step up and we think they can if we need them to," Parker said. "They've not had many, or really any, reps with the (first team), so that's the first thing.
"They've also got to be able to pick up things quickly because we may need them in less than two weeks."
Another Razorback, redshirt freshman defensive end Derek Moore, also was carted off from Tuesday's practice with what was diagnosed a sprained left ankle. He has five tackles in three games this season.
After starting three games at tight end, redshirt freshman Payne Hall has been moved to inside linebacker this week. He spent time there in the spring before switching to tight end because of injuries.
"It's just something we're looking at," said tight ends coach Clifton Ealy.
Hall, a redshirt freshman who played safety at Muldrow, Okla., said the coaching staff didn't specify a reason for the move. He did suffer a shoulder injury on the opening kickoff against Alabama.
"I really don't know what's going on," Hall said. "I haven't played tight end since (the Lousiana-Monroe) game."
Another move was made Tuesday when junior Justin Slaughter switched from fullback to tight end to "give him a look" at that position.
Arkansas quarterback Matt Jones suited up, but didn't throw much during Tuesday's practice.
Jones took several solid hits during Saturday's game and had visible bruises on his right (throwing) arm after the game.
"Matt's just really bruised up and we got him out here and started him on some fundamentals, but he's just so sore," said Arkansas coach Houston Nutt.
Jones downplayed the soreness, saying it was nothing to worry about and he'll be ready to go against Auburn.
"Everything's cool," Jones said. "My arm's not messed up. People are saying stuff like I'm hurt, but they're tripping out ... I'm fine.
"I'm just chillin'."
Skinner On Ice
Arkansas punter Jacob Skinner rested Tuesday while Jeremy Davis, a true freshman from Fort Smith, made all the punts.
Skinner -- who's been nagged by tendinitis in his right (kicking) knee since preseason practices -- mishandled a snap at Florida and has had problems the past three games with consistency on his drop.
He still averaged 40.1 yards on seven punts against the Gators to improve his average to 37 yards per punt this season.
"We're resting Jacob a little bit and letting him concentrate on catching the ball and dropping the ball," Nutt said. "We don't even care if he kicks all week. Catch the ball and drop the ball correctly all week long."
Defensive back Chris Houston said he's about "97 percent" healthy now after missing the past two games with a high-ankle sprain ... Nose guard Titus Peebles spent time with the first team Tuesday in place of regular starter Jeremy Harrell ... Senior Elliot Harris was with the first team at defensive end in place of regular starter Marcus Harrison.
Tubbs Suffers Broken Ankle
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