The now-37-year-old quarterback played against the New England Patriots in the AFC Championship Game six days after suffering a torn ACL and meniscus in his right knee.
Although the Chargers lost 21-12, Rivers limping through the game sealed his status as one of the toughest players the league has seen. He has continued to prove it in every game since, with his active streak of 208 consecutive regular-season games played the longest in the NFL.
Rivers didn't have one of his best games that Sunday in 2008, completing just 19 of 37 passes for 211 yards, with no touchdowns and two interceptions, as the Chargers failed to score anything but field goals.
But 11 years later, he finally gets another postseason shot at Tom Brady when the Chargers visit the Patriots on Sunday (1:05 p.m. ET, CBS) in a divisional-round playoff game. A win would return the Chargers to the AFC title game for the first time since Rivers' ACL game.
"The fact that he played was unbelievable," Brady said. "They played a good game. We made a few plays, got a couple turnovers from them. It ended up being a tough game. It was a hard-fought win.
"There's a reason why both teams are playing here this weekend -- because we've earned it and put ourselves in position for a great opportunity. Both our teams want to win, and it's going to be a tough game, regardless of the outcome."
Two graybeards, Rivers and Brady will have a combined age of 78 years and 198 days on Sunday, making it the oldest combined starting quarterback matchup in postseason history.
Back in January 2008, Brady was 30 and in his eighth NFL year and Rivers was 26 and in his fourth. The Patriots were at the end of a perfect season and trying to cement their status as one of the greatest NFL teams ever by reaching and winning the Super Bowl.
However, an injured Rivers, playing with a balky knee, stood in their way.
"Honestly, it wasn't crazy pain," Rivers said about playing with the injury. "It kind of buckled a few times in the game, but I really was thankful. Throughout the course of the game, I didn't feel like it hindered me as much as I anticipated.
"We didn't have our best day. It didn't help, but we didn't have our best day, and I really don't attribute it to that."
In addition to Rivers' injury, running back LaDainian Tomlinson had a sprained medial collateral ligament (MCL) and tried to play, but he was unable to make the cuts he normally made and gave way to Michael Turner.
According to Dr. David Chao, the Chargers' head team doctor at the time, Rivers and Tomlinson were not the only players dealing with injuries.
Tight end Antonio Gates was hobbled and needed reconstructive surgery on his big toe. Fullback Lorenzo Neal (fibula fracture) and center Nick Hardwick (Lisfranc injury) had recently come back from surgeries.
And outside linebacker Shawne Merriman had put off reconstructive knee surgery that ultimately led to his career being cut short.
"We really were in bad shape going in there as a collective unit," Rivers said. "So, yeah, we had some guys with some things [back then]."
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After suffering the knee injury in a 28-24 playoff win at the Indianapolis Colts in the divisional round, Rivers was insistent that he would play against the Patriots the following week.
Even as fans taunted him when he walked off the field to the locker room at the RCA Dome, Rivers told them, "I'll be back."
Rivers was right.
"That entire week was really interesting because a lot of people on our team didn't know that Philip even had an ACL tear," Hardwick said. "We knew that he had surgery and that he had to unlock his knee.
"And we knew he wasn't going to be out to practice until at least Friday, maybe not going to be available until the walk-through on Saturday, but we all understood that he was going to play. And I don't think there was ever any doubt he was going to play."
Thousands of fans waited to greet the players upon their return to Chargers Park from Indianapolis on that Sunday, but Rivers managed to slip through the back of the facility unnoticed, get into his truck and get an MRI that night, confirming the ACL and meniscus tears.
The Chargers had a competent backup the team trusted in Billy Volek, who finished out the game against the Colts. However, Rivers didn't want to miss a chance to reach his first Super Bowl, so he pushed to play.
After receiving the MRI Sunday evening, Rivers had to make a decision on whether to have arthroscopic surgery the next day to repair the torn meniscus to unlock his knee.
Rivers met with the team's medical staff and coach Norv Turner, remaining insistent that he would play.
"People ask about teams and coaches forcing players to play hurt," Chao said. "But in my experience, it's the players themselves that force themselves to play. Norv wasn't telling Philip to get the surgery and come back quickly. He was like, 'Take your time, Philip, we got you. You've got a long career, Billy's got this.'
"But Philip remained steadfast to do what it took to play, and we moved forward with surgery."
So how hard is it to play with a torn ACL?
"You could call the ACL an internal seat belt," Chao said. "No question, you can drive your car without a seat belt on and get away with it. But in the NFL you're racing NASCAR, and you better have your seat belt on.
"So it's not normal to play without an ACL. In Rivers' case, we had him in some special bracing that we felt could temporarily keep him safe. But even then, we made him aware of the risks, and he wanted to play."
Hardwick said Rivers appeared to manage the injury well for the most part.
"I don't remember anything about him not being able to execute his job," Hardwick said. "It was pretty remarkable what he was able to do in such a quick turnaround. Not only having an ACL tear, but having a meniscus cleaned out the week before. It's pretty gritty.
"That's Philip. We knew it meant so much to him that he was going to find a way to get it done. He was not going to let this moment pass him by."
Throughout his 15-year career, Rivers has dealt with his fair share of injuries but has always answered the bell.
Rivers played through a chest injury and bulging disk in his back during the backstretch of the 2014 season, missing his first practice since 2007.
Rivers also was diagnosed with his first concussion during the 2017 season and did not clear concussion protocol until Friday, two days before taking the field against the Buffalo Bills in a 54-24 victory in Week 10.
A devout Catholic who has always been outspoken about his faith, Rivers wears a medal around his neck of St. Sebastian, the patron saint of athletes. Leading up to the playoff game against the Patriots more than a decade ago, a concerned Rivers was buoyed by a comment over the phone from his mother, Joan, who reminded her son that St. Sebastian's feast day was Jan. 20, the day of the Patriots game.
"The week following [the Colts] game was a very spiritual one for me," Rivers told the National Catholic Register. "... Amazingly, maybe even miraculously, I was able to play [against the Patriots]."
Rivers knows the numbers.
He's 0-7 overall against Brady, a future Hall of Famer and the GOAT. That includes an 0-2 record in the postseason, with Rivers completing only 48 percent of his passes, with no touchdowns and three interceptions.
The Patriots have won eight straight playoff games at Gillette Stadium, the fifth-longest home playoff win streak in league history, according to the Elias Sports Bureau.
New England is 8-0 at home this season.
However, Rivers says this season is a new year, and the Chargers are 9-0 when boarding a plane this season.
"This team is 0-0," Rivers said. "We've never played them. Certainly, I was a part of all those teams that didn't win in those games, but this team right here has never played them, and that's the way I look at it."
Hardwick remembers the confetti falling from the sky at the end of the 2008 game and his former college teammate and Patriots offensive lineman Matt Light celebrating a return trip to the Super Bowl as he watched from the sideline.
He's looking forward to a better result for his former team this time around.
"We had our chance at them and we were unsuccessful," Hardwick said. "For me as a former teammate of a couple of these guys and a fan of the rest of them, I really just wish them the best of luck. And I hope they go there and can execute their assignments and keep their emotions in check enough to be able to fulfill their potential.
"I really do feel that this is the best-coached Chargers football team that I can remember in quite a long time."