SAN DIEGO (AP) Chargers center Rich Ohrnberger didn't practice Friday because of a sore back.
Ohrnberger has replaced San Diego center Nick Hardwick, after the Pro Bowler suffered a season-ending neck injury on Sept. 8.
So Ohrnberger's availability when the Chargers host the Jacksonville Jaguars on Sunday is crucial.
If Ohrnberger, who is listed as doubtful, can't go, rookie Chris Watt is his likely replacement.
''I'm excited if the opportunity presents itself but we'll see,'' Watt said. ''I'll be ready to go if they put me in there.''
Watt is a third-round pick out of Notre Dame. He had a spirited camp battle with Johnnie Troutman at right guard, but Watt also took snaps at center.
''Being able to work a few preseason game there, I think really helped in being comfortable at the position,'' Watt said. ''If I get an opportunity on Sunday it won't be my first time going through it.''
Veteran center Doug Legursky is another option if Ohrnberger is down.
Ohrnberger's status probably won't be determined until Sunday morning.