According to UT-San Diego San Diego Chargers beat writer Michael Gehlken, center/guard Rich Ohrnberger will undergo back surgery miss the remainder of the season.
Ohrnberger has struggled to play through nagging back injuries all season long, finally giving up his starting spot to rookie center/guard Chris Watt on Sunday in a win over the St. Louis Rams.
Ohrnberger is the third starting center to go on IR for the Chargers this year, following the early-season exits for Nick Hardwick and Doug Legursky. Hardwick is expected to announce his retirement at the end of the season.
Chris Watt may have been drafted as the eventual replacement for Hardwick, but nobody expected it would happen this soon. Now, the fate of the interior offensive line (and, really, the team's playoff hopes) rest firmly on his shoulders.
The team has not yet announced the corresponding move to fill the roster spot, but undrafted rookie guard Craig Watts is the likeliest candidate for promotion.