The Titans (2-1) had lost nine straight to San Diego in the skid before Locker connected with Hunter for the rookie's first NFL catch.
"Honestly, once I threw it and saw them both jump to go up for it, it was so much higher than the guy guarding him, I started celebrating," Locker said of his winning pass.
Locker ended the slide by completing seven passes to six different receivers for 94 yards on the game-winning drive.
The eighth overall draft pick in 2011 finished with 299 yards passing and also ran for 68 yards and another touchdown.
"That's a huge game for him and this football team again," Munchak said of Locker.
The Chargers' final play featured seven laterals and even a kick of the ball, trying to keep it alive, before the game ended.
San Diego (1-2) led most of the game despite being banged up. Three starters were out because of injuries, a fourth was very limited and a fifth was lost to an injured foot in the first half.
Tennessee overcame a missed field goal and 10 penalties for 110 yards in the first half.
The Titans were flagged only once in the second half. They also lost two timeouts in the second half when Munchak lost replay challenges.
But Tennessee blocked a 38-yard field goal attempt by Nick Novak to end the first half, and the teams were tied at 10 at halftime.
"They did take a touchdown off the board there," Rivers said. "I haven't seen the replay to know if it was the right call or not. Obviously, that's why I was so upset. That was a big play in the game when a touchdown gets called back."
San Diego settled for a 44-yard field goal by Novak for a 10-3 lead late in the second quarter.
The Titans had their chances as well. Hunter nearly had his first NFL catch and touchdown in the second quarter, except a defender got an arm in early.
NOTES: Rivers had been 6-0 against Tennessee ... The Titans have yet to turn the ball over this season ... The Titans are 4-1 when Locker has a passer rating of 90 or higher. He finished with a rating of 96.6 ... The Titans have won three of their past four home openers ... San Diego left tackle King Dunlap also got hurt late, but McCoy said he hadn't heard about all the injuries yet.
Copyright 2013 by The Associated Press