It wasn't long ago that Philip Rivers was known for leading the San Diego Chargers to AFC West titles, and his name was routinely mentioned among the upper echelon of NFL quarterbacks.

But lately, Rivers has been known more for interceptions and fumbles, as the Chargers fell from the top of their division and into a complete regime change, with the firing of the head coach and general manager after missing the playoffs the past three seasons.

But Rivers, 31, seems determined to show he can be a better version of the quarterback that once led the NFL in passing yards (2010) and touchdowns (2008), and not the one who threw 25 interceptions, lost 12 fumbles and was sacked 79 times in the past two seasons.

He told USA TODAY Sports he has been reinvigorated by the new offense of head coach Mike McCoy and offensive coordinator Ken Whisenhunt.

"I think my best football is ahead of me, I really do," Rivers said. "That's being optimistic, because we've had a lot of really good years. I am probably on the second half of my career, the back end, but I think I've got a lot of good football left.

"To me, the bad is always magnified (more) than the good, and there has been some bad. But there has been a heck of a lot of good."

With A.J. Smith, the general manager who traded for Rivers during the 2004 draft, head coach Norv Turner, who called plays for Rivers for the previous six seasons, and many of the most famous Chargers faces gone, Rivers is facing a pivotal moment: He must show his new bosses he is still the franchise quarterback and the right player to lead the Chargers back to the postseason.

"This next year or these next two years, Philip Rivers' career and his legacy depend on how he performs. Because right now, if he doesn't win or change this around, he's the one who is going to become expendable," former San Diego Chargers fullback Lorenzo Neal, who played with Rivers from 2004 to 2007, told USA TODAY Sports.

"This new regime, they want to win. Philip Rivers is not the head coach's guy. He can become that guy. Philip understands what's at stake. He understands if he wants to become an elite quarterback, he's going to have to put some numbers up. No question, this is a crossroads year for Philip. And if you asked him, he would tell you, 'I can't afford to have another two years like I had.'"

When Rivers met with McCoy and Whisenhunt this spring and watched cut-ups of game tape over his seven years as the starting quarterback, he was prepared to be highly critical of his play, especially as he looked at each of his 15 interceptions last season. Were they the results of bad decisions, bad throws or bad luck?

"Poor throws are things that happen," Rivers said. "It doesn't mean they're OK, but it happens. And then the others ones are, 'Was that a poor decision? Was it a careless mistake?' Those are the ones I really focus on. There haven't been as many as you would think.