SAN DIEGO -- Philip Rivers inspects the scars on his surgically repaired right knee and can't help but marvel at how minuscule they are.

It helps the Chargers' quarterback appreciate the advances of modern medicine. The surgical marks from the anterior cruciate ligament surgery he underwent are much different when compared with the ACL operation his father, Steve, had some 37 years ago.

"I've got a little tiny scar that's probably 2 inches, maybe a little longer, and he's got one on the inside of his knee that's kind of a horseshoe shape," Rivers said. "It's amazing what the difference is."

Six weeks after undergoing surgery, Rivers is rehabilitating the knee like a madman, intent on recovering by the time training camp begins in late July.

His father? Well, he was in a hard cast that stretched from hip to toe six weeks after his ACL procedure.

"I wake up from a surgery in a machine that's bending my knee back and forth," Rivers said. "He had to have his immobilized for six weeks."

Rivers plans to return to the football field just more than six months after the injury, which he suffered in the Chargers' playoff victory over the Indianapolis Colts on Jan. 13. And he doesn't expect to be there only in spirit.

"I would be totally shocked if I'm not ready for training camp," Rivers said. "Obviously, I'm going to be wearing a brace on that knee all year long. Other than the brace, if you come to watch practice the first day of training camp, this is my opinion: I'd be shocked if you could say, 'Aw, he looks a little off, he looks a little different.'

"So I expect to be rolling by training camp."

Rivers will soon start doing exercises in a swimming pool and could receive the go-ahead to begin running by the end of this month. He has been doing a variety of exercises to regain strength in the knee and the muscles in other areas of the leg.

The rehabilitation routine includes riding a bike along with leg presses, calf raises and hamstring curls. Rivers said a major emphasis is being placed on balance-type exercises.

The Chargers re-signed backup quarterback Billy Volek last week, but the urgency to retain Volek wasn't because the club has concerns over the recovery of Rivers' knee.

"Medically, I'm told it's fine and that he's going to be OK," general manager A.J. Smith said. "I'm very pleased with what they're telling me."

Rivers left the playoff game against Indianapolis after throwing a 56-yard screen pass for a touchdown to Darren Sproles on the final play of the third quarter. He landed awkwardly after feeling the knee give out as he jumped to throw the pass.

But Rivers said he believes the ACL was already starting to tear earlier in the game. In the second quarter, while scrambling to his left, he was hit from behind and felt a twinge in the back of the knee. He later felt "two pops" while throwing a third-quarter scoring pass to Chris Chambers.

Rivers said trainer James Collins examined him after both instances and detected nothing.

"They do all the tests," Rivers said. "They have all these manual hand tests to check the stability of all ligaments. It was fine. I put a sleeve on it. It was nothing terrible. It was just weird.

"Then on that screen pass, it just went all the way. I'm not sure if I was just slowly tearing that thing the whole game or what. I have no idea."

Later that night, an MRI exam revealed that he had torn the ACL and suffered cartilage damage.

Rivers, Collins and team doctor David Chao stayed at Chao's office until 1 a.m. trying to determine what could be done to get Rivers healthy enough to play in the following Sunday's AFC Championship Game against New England.

Rivers returned to Chao's office at 8 a.m., and the decision was made to perform arthroscopic surgery to repair the cartilage damage and hope that the procedure would enable Rivers to play against the Patriots.

The rehab process lasted nearly 24 hours a day. Yes, that includes when Rivers was trying to sleep at night.

"Between everything we were doing with the trainers at the facility, I pretty much slept on the floor in two different machines," Rivers said. "One machine that made my knee bend and another machine that iced me all night long. That's where I gave myself a chance to play."

Rivers played decently, but the wounded Chargers -- running back LaDainian Tomlinson (knee) and tight end Antonio Gates (dislocated toe) were also ailing -- fell short against New England.

Looking back, Rivers said he learned a lot from his second campaign as an NFL starter. He was turnover-prone early in the season as the Chargers struggled out of the gate before playing much better over the season's second half.

"I think I learned a lot about myself," said Rivers, who threw 21 touchdown passes to go with 15 interceptions and six lost fumbles. "I had a false sense of what it's like to be a quarterback in this league from the previous year. We had some highs and lows. I didn't play great all the time, but we were 14-2.

"It was kind of like, 'Oh, he's a first-year starter,' so nothing I did was really my fault even though I had some poor plays and poor games.

"I think this year it was a little different. I think I grew a lot and I appreciate going through that, I really do."

Contact staff writer Mike Sullivan at (760) 739-6645 or msullivan@nctimes.com. Comment at sports.nctimes.com.