Hardwick, the team's most experienced offensive lineman, agreed to a three-year contract with the Chargers on Tuesday, just before he was scheduled to become an unrestricted free agent.
"It's huge," said Hardwick, who's entering his ninth season. "You just never know how it's going to unfold. Both sides kept working really hard. It got to the point where everything looked good and we said, 'Let's go with this.' Ultimately, I'm very excited to be here. This is where I want to be. I want to finish it out here. That'd be a nice run."
At about the same time, the Chargers released left tackle Marcus McNeill due to a history of neck injuries and to clear cap space. There's still a chance the Chargers could re-sign McNeill, a second-round draft pick in 2006 who played in two Pro Bowls. McNeill missed the final seven games of 2011 with a neck injury.
McNeill had to pass a physical by Thursday to qualify for his $10 million salary.
However, McNeill's agent, Alvin Keels, told ESPN's Josina Anderson that his client was cleared to resume playing after seeing a doctor last Friday.
Tuesday's move came less than two weeks after Hardwick's good friend, four-time Pro Bowl left guard Kris Dielman, retired after nine seasons due to the effects of a concussion.
It would have been a huge blow if Hardwick had left as a free agent.
"That's a lot of years of experience that would have been gone out the window," said Hardwick, who's been to one Pro Bowl. "I'm just excited to be back, to keep growing. We've made some really good strides here the last few years, as far as our abilities on the offensive line. We need to take this thing to another level, to keep evolving as a line and a unit."
The Chargers would like to re-sign left tackle Jared Gaither, who helped stabilize the line in the season's final five games after he was waived by Kansas City. Gaither became an unrestricted free agent on Tuesday afternoon, as did star wide receiver Vincent Jackson, who signed a five-year, $55.55 million contract with Tampa Bay.
The Chargers missed the playoffs the last two seasons.
"I'm just glad to be back and have a chance to work with Philip Rivers for the next several years and work with the guys on the line," Hardwick said. "We can make some pretty good waves. We have a lot of room for improvement.
"It's going to be exciting, and we'll see how good we can get, and we have to get good in a hurry. We can't flop around at the first of year. We have a lot of hard work ahead."
San Diego tendered contract offers to restricted free agent Brandyn Dombrowski, an offensive lineman, and exclusive rights free agents Richard Goodman, a wide receiver, and Mike Windt, the long snapper, maintaining negotiating rights with the three players. Should Dombrowski receive a contract offer from another team, the Chargers will have a chance to match the offer. As exclusive rights free agents, Goodman and Windt cannot sign with another team.
Information from The Associated Press was used in this report.