Concerns are starting to mount that the O-line will not be able to protect the blind side of QB Philip Rivers.

But don’t tell Rivers because he wouldn’t listen anyways.

 “As a quarterback you never worry about what is going on up in front of you,” Rivers said. “I don’t drop back with any thought in mind of who is where.” 

Rivers will not openly say he is concerned about his protection. But a look at what has happened, and he should be.

San Diego is without Pro Bowlers LG Kris Dielman (concussion) and LT Marcus McNeill (neck). Both suffered career ending injuries last season. They were just two of several injuries that left the O-line in shambles for most of 2011. 

Rivers was sacked 28 times and threw 17 INTs through the first 12 weeks of the season. In week 13, LT Jared Gaither (released from Chiefs ) was signed and LG Tyronne Green (broken finger) returned to action. Rivers was only sacked two times and threw three INTs for the remainder of the season. Rivers finished the year with a career high 20 INTs.

General manager A.J. Smith and coach Norv Turner are confident the O-line issues were resolved with the addition of Gaither and a healthy Green. But Gaither (back spasms) was carted off the field in the first full practice of training camp. He has only participated in a few walk-thrus and has not been seen by the media in over a week.

“He is going through some treatments,” Turner said of Gaither on Monday. “He has seen a doctor. I can tell you if he has made progress in the next couple of days.”

Rookie G Johnnie Troutman (round five, 149th overall pick) was expected to be boost to the line. But he tore a pectoral muscle a few days before the draft and has not participated in any workouts. He is expected to be healthy enough to play by mid October but will likely be placed on the IR list at the start of the season to free up a spot on the 53-man roster.

Reserve G-T Brandyn Dombrowski (foot, cyst) has not passed his physical and also appears destined for the IR list.  LT Mike Harris (undrafted, UCLA) has seen the baulk of the snaps with the first-team in the absence of Gaither.

His inexperience showed in the first preseason game against the Packers. TE Randy McMichael had to help Gaither by chipping pass rushers trying to make their way through Harris. 

“He is a young player that is going to improve," Rivers said of Harris. "A guy who is in his eighth, ninth, tenth year, the improvements are not going to be as drastic. As a rookie you can drastically see a difference in a month’s period of time. I think he is in the boat were each and every day he gets better at something.” 

While this sounds like a glowing review of the progress Harris has made, an easy read between the lines reveals Harris is not nearly as good as former Pro Bowler McNeill, or a healthy Gaither.

To make matters worse, Green’s right foot was stepped on in practice on Tuesday and he wore a boot afterwards. A prognosis of the injury has not been given.

 No Green and no Gaither would put the Chargers back to where they were midway through last season when they were missing Dielman and McNeill. Nevertheless, Rivers will continue to embrace whoever is put in front of him.

“You got to go play,” Rivers said. “We have dealt with injuries here in the past years and in the past year more than any other.”

This includes the O-line in its current form with an undrafted and unproven rookie protecting his blindside.

“It’s doing good,” Rivers said of the O-line. “It is doing real good.”

 Follow the Chargers and Dan McLellan on Twitter @CBSSportsNFLSD and @sandiegosports.