Passion and purpose: Chargers' Philip Rivers leans on mother's credo to finish 2019

COSTA MESA, Calif. -- For the eighth time in the past 10 seasons, Philip Rivers and the Los Angeles Chargers will not reach the postseason.

The Chargers have not won the AFC West since 2009, so Rivers has grown accustomed to manufacturing things to play for at the end of the year.

But as he prepares for his 224th consecutive start, Rivers said he will not lack for motivation when the Chargers hit the road to face the division-leading Kansas City Chiefs on Sunday (4:25 p.m. ET, CBS) still looking for their first AFC West win this season.

"This is our last chance together to go finish it off the right way," Rivers said. "I just look at that as another opportunity. I'm thankful to have it in one of my favorite and one of the best NFL environments to play in. Really, I'm just trying to keep it as singularly focused as that -- a chance to play the Chiefs in a National Football League game."

A razor-sharp focus and passion are characteristics that were fostered in Rivers at a young age by someone just as competitive as he is -- his mother, Joan Rivers.

Joan Rivers works as a middle school teacher at St. Ann Catholic School in Decatur, Alabama, teaching math and religion.

"We play four square, and I play to win, not for fun," Joan Rivers said, chuckling. "They didn't know me when I first started teaching there, and they'd say, 'Let's go play four square.' And they didn't realize that I was going to be slamming the ball at them."

Joan Rivers says she prays a lot when watching her son play, whether it's in person or on TV.

"Sometimes I pray about things that I don't know if it's OK to pray about, like, 'Is it OK to pray that he never throws another interception in this game?'" she said with a laugh. "It's been fun, and it's going to be so bittersweet when it's over because you can relax a little bit, but I know how much he loves the game, and we all do.

"But I do pray a lot during the game because I've just seen so many injuries and we haven't got time for injuries. We need Philip upright. Other than that, I'm real nervous during the game because I want him to win so bad, and I am competitive. I'm just so pleased with everything that has happened in his life. He's just been such a good role model for his brother and sister, and for even us. He's such a good leader. He leads our family, in a way. And I think people like for someone to get out there and say, 'Let's go.'"

Joan Rivers penned a book with fellow teacher and friend Patrice Lappert titled "Philip Rivers: Passion and Purpose."

The children's book focuses on how Rivers balanced his family and Catholic faith growing up and throughout his NFL career.

"Passion and purpose is how he has done things from the beginning," Joan Rivers said. "You just knew that he had a passion for everything. Not just a passion for football, but for whatever he does -- he's not going to do it without a purpose. And I can say he got that from me."

Rivers looks to finish 2019 on a high note in perhaps his final game in a Chargers uniform. And when taking the field at Arrowhead Stadium, Rivers will think of those two words from his mother -- passion and purpose -- that have served as a constant reminder over the years. Rivers said both of his sons, Gunner and Pete, have read the book, sharing it with the rest of his family and friends.

"It was a combination of both her and my dad [Steve Rivers]," Rivers said. "I think it's an easy read. Both my boys read it, but they know the stories. And I think that's what she was hoping for. You never know who it can impact."