The matchup to watch in Thursday night's Falcons-Bengals preseason opener will be Atlanta right tackle Lamar Holmes against Cincinnati defensive end Robert Geathers.
Holmes will start after Mike Johnson dislocated his left ankle and broke his left leg in Tuesday's practice. Johnson will have surgery next week.
"It's a terrible thing that happened with Mike," Holmes said Wednesday. "Mike is a great guy and a great teammate. Mike helped me a lot.
"It's part of the game. Coaches tell you all the time, you're one play away from being a starter so you have to always prepare like you are the starter. It's something we have to do."
Johnson played in every game, including one start, in 2012. He entered training camp as the favorite to replace Tyson Clabo, who signed with Miami after being released by Atlanta.
The injury leaves Atlanta with almost no experience at the position.
Holmes played in only one game as a rookie last season after missing training camp with a foot injury. Geathers, entering his 10th season, will be a tough test for such an inexperienced player.
The matchup will help the Falcons determine if they need to look for a veteran tackle. Falcons coach Mike Smith said he's Holmes (6-6, 333), a third-round pick from Southern Miss in 2012, can handle the job.
"He's a big, athletic tackle," Smith said. "That's what you want. There are very athletic pass rushers we're going to face all season long. That's probably his strength. He's very athletic."
Ryan Schraeder, an undrafted rookie from Valdosta State, will play behind Holmes.
"You kind of have to keep your head down and move on and we're going to have to have some young guys step up," said Falcons quarterback Matt Ryan. "That's what it takes. Every team deals with it. Every organization deals with it. I think our young guys will do a good job.
"I think Lamar has done a really good job this camp and really this offseason, too. He's gotten himself into really good shape."
Smith said it's too early to rule Johnson out for the season. He said another offensive lineman will begin cross-training at right tackle.
Most starters, including Ryan and Bengals quarterback Andy Dalton, are expected to see only limited playing time.
Bengals coach Marvin Lewis said he'll be looking for players to emerge in the game who are trying to win roster spots.
"We know who our quarterback is going to be, we know who most of our skill guys are," Lewis said after Wednesday's light practice.
"We know basically who the starting group is going to be so you're battling for guys to fit into new spots, special-teams wise. You allow some attrition, some graduation every year, so we can plug in some younger guys. We're looking for those guys to step up and play."
The Bengals shared the practice fields with the Falcons on Monday and Tuesday. The teams dodged the rain by holding separate workouts in the Falcons' indoor facility on Wednesday.
Lewis said the combined practices were a success.
"It's been great," Lewis said. "The Falcons' hospitality and Mike's organization, it's been outstanding. It's been real positive work and productive work for us."
Among players being held out with injuries Thursday night are the two top receivers in the 2011 draft, Cincinnati's A.J. Green and Atlanta's Julio Jones. Green remained in Cincinnati this week to receive treatment for his bruised knee. Jones will be held out with a tight hamstring.
Falcons outside linebacker Sean Weatherspoon (dislocated left finger) and Bengals left tackle Andrew Whitworth (knee) also won't play.