Falcons tackle Mike Johnson played in only 18 games with one spot start over three seasons, but that makes him the veteran among the players vying to replace departed starter Tyson Clabo on the right side.

Now Johnson likely is out for several months after he suffered a fractured fibula and dislocated ankle in his left foot during practice Tuesday. Falcons general manager Thomas Dimitroff already was making calls Wednesday about signing a veteran free-agent tackle to the roster.

The Falcons have about $7.5 million available in salary-cap space, according to NFLPA documents, so they could easily make such a move. The problem is that there isn’t much talent on the market right now with most NFL teams carrying 90 players in training camp.

For now it appears the Falcons will evaluate their inexperienced tackles to see if one of them can fill in for Johnson. They will get their first chance in live action this preseason Thursday in the exhibition opener against the Bengals at the Georgia Dome.

“Now that we lost Mike, someone else is going to have to step up and compete,” Falcons coach Mike Smith said Wednesday. “We’ve said from the very beginning we really like the young college free agents and how big they were, and they’ve really done a nice job. They are going to get an opportunity now to get on tape a whole lot more than they would have yesterday.”

Johnson is scheduled for surgery next week. Smith said he didn’t know how long Johnson would be out, but according to the American Academy of Orthopaedic Surgeons, Johnson’s injury typically requires several months of rehabilitation before the patient can return to competitive sports. The Falcons open the 17-week regular season Sept. 8.

Sam Baker, the left tackle, now is the only healthy player on the roster with an NFL start at offensive tackle. That’s why the Falcons are looking at the free-agent market for a possible addition.

“I know Thomas and his staff always have a list together,” Smith said. “If we feel and deem that is something we need to do, we will do it.”

The Falcons have inquired about free-agent tackle Travelle Wharton. Wharton started 99 games for the Panthers from 2004-11, but missed the 2012 season after suffering a torn ACL while playing an exhibition game for the Bengals last summer.

Other veteran free-agent tackles include Sean Locklear (92 career starts), Winston Justice (43), Jared Gaither (37), Frank Omiyale (33) and Wayne Hunter (25). The agent for Jammal Brown, a former Pro Bowl tackle for the Saints, said his client is retired after missing last season with a hip injury.

Lamar Holmes will get the first opportunity to replace Johnson. The Falcons selected Holmes in the third round of the 2012 draft out of Southern Mississippi, and he played only seven snaps from scrimmage as a rookie after being slowed by a foot injury that forced him to miss the offseason program.

At Wednesday’s practice, Holmes and undrafted rookie Ryan Schraeder took snaps with the starters at right tackle. Smith said Holmes would get the majority of the snaps with the starters in the game Thursday, but added that “moving forward, I couldn’t say.

“We drafted Lamar in the third round and anticipate he is going to do the job,” Smith said. “There are some young guys I am anxious to see how they are going to do. We’ve got a long time, four (exhibition) games, to evaluate.”

Smith said athletic ability probably is Holmes’ strength. That’s an important attribute for right tackles who must pass protect against quick defensive ends.

Smith said strength also is important because left defensive ends tend to “bull rush” more often than right defensive ends. Holmes is listed at 6-foot-6, 333 pounds and Schraeder at 6-7, 300.

Schraeder said he’s still learning the details of the offense, but thinks he has a pretty good grasp of it. He played in a spread offense at Division II Valdosta State.

“In that aspect there are a lot of similarities as far as throwing the ball a lot,” Schraeder said.