BOURBONNAIS, Ill. -- The 34 points the Chicago Bears piled up in their preseason-opening win over the Philadelphia Eagles masked at least one offensive problem they might face for the foreseeable future.

The Bears ran the ball with starters and second-team players for only 16 yards on 12 carries in the first half of their preseason opener and had negative yardage on the ground through much of the first half. Right tackle Jordan Mills has his left foot immobilized in a light plastic cast this week, and the right side of the line is struggling for continuity.

Considering the team is without Mills and that right guard Kyle Long missed almost all of training camp with a viral infection, it is easy to see how the ground attack could suffer.

"We're trying to jell with whoever we have in there and just get used to playing beside anybody because you never know what's going to happen throughout the course of a year," left tackle Jermon Bushrod said.

The offensive line showed little problem adjusting to subs being on the field during pass-blocking situations, but blocking for the ground game wasn't as effective. Running backs Matt Forte and Shaun Draughn struggled to get out of the backfield without being hit Friday.

Coach Marc Trestman acknowledged the importance of continuity for run-blocking.

"I say this all of the time, whether you're a first-year player or a 10-year player: 'You've got to practice, you've got to work every day,'" Trestman said. "That's why you see (veteran center Roberto) Garza out there every day working. He's a guy who's played longer than anybody, and I'm talking offensive line."

Last year, the Bears' offensive line went through the entire season without missing a start. Mills sustained a foot injury during the season finale against the Green Bay Packers, and Eben Britton replaced him.

So far this season, Chicago hasn't had the full line together for a single day of camp, and much of the time the backups were unavailable.

"If you can have five guys get through a whole year starting, especially on offensive line, that's a blessing," Bushrod said. "If we can have three or four being constant, that's a win for us. If we can just keep as many guys on the field as we can, that's our goal, that's our plan.

"But this is a tough game, you have to be a little lucky when it comes to the injury bug."

The Bears possess better depth throughout the roster than they did last year, but the numbers are starting to be thinned. Britton, a swing tackle who also can play guard, but has been out since July 30 with a hamstring injury. Chicago turned to using former CFL player Michael Ola at right tackle.

The loss of backup center Brian de la Puente on Saturday to a grade 2 knee sprain that could keep him out for a few weeks further depletes the line depth. The former New Orleans Saint, also a backup guard, started Saturday's game as a replacement for Long, who returned to practice last week from his illness and quickly twisted an ankle.

"I think it's part of football," Trestman said of the injuries. "Kyle is back. ... We expect Jordan to be back soon. We're keeping our fingers crossed with Brian.

"It's giving other guys an opportunity to get a lot of work done. It's football. These things happen."

The real problem for the Bears will show if the line starts to develop cracks in pass protection and quarterback Jay Cutler is in jeopardy as a result.