SAN DIEGO >> Antonio Gates first arrived at Chargers Park in 2003, and Philip Rivers joined him one year later on the peaceful practice fields and low-slung buildings tucked below a golden hillside on Murphy Canyon Road.

The tight end and his quarterback have spent their entire NFL lives inhabiting this training complex in northern San Diego. They’ve honed their skills with uncountable thousands of throws and catches on these fields, and they’ve built warm friendships with hundreds of their fellow Chargers in its locker room.

But Chargers Park and San Diego are down to their final week as this team’s home. After a three-day mandatory minicamp concludes Thursday, the players will disperse for summer vacation before the moving vans portentously parked outside the complex are filled for the 85-mile drive north to Costa Mesa, the Orange County city where the Los Angeles Chargers will hold training camp in July.

“It’s a bittersweet moment, because obviously the memories are still here,” Gates said today. “They will forever be here for myself, for the guys that have been around.”

Chargers Park will be empty this summer for the first time in two decades, and San Diego will spend its autumn Sundays without the team that arrived from Los Angeles in 1961. The move has loomed for five months, but its imminent finality has some veterans feeling nostalgia during their last few workouts in San Diego’s postcard-perfect sunny weather.

“There’s a lot of time spent out there, a lot of balls thrown,” Rivers said while standing in the cool shade just off the practice fields. “A lot of time spent in this locker room, weight room, meeting room. Qualcomm (Stadium) and the memories there from game days are public memories that a lot of people shared in. But shoot, I don’t know how many days — probably almost close to 300-plus a year — we’ve been coming in here in some capacity.”

While coach Anthony Lynn and many current Chargers haven’t been around long enough to truly feel their fans’ pain, the senior players and team employees are still processing the end of this era.

“You’ve got to look at it as a positive, as we’re going somewhere to a new beginning,” said pass rusher Melvin Ingram, who has spent his entire five-year career with the Chargers. “But you’ve also got to have a bitter feeling, (because) this is where it all started, and you’re leaving the place where it all started.”

While the Rams packed up swiftly in St. Louis after securing relocation last year, the Chargers elected to make a slower transition north, holding their offseason workouts and running out their lease at the training complex still owned and maintained by the city of San Diego.

Rivers was grateful for the gradual breakup, which allowed him extra time to decide whether to commute to LA or to move his wife and eight children out of their longtime family home.

Rivers still hasn’t decided, by the way.

“I will figure it out at some point,” he said with a laugh.

The Alabama native had never been west of the Mississippi River when the Chargers acquired him in a draft trade. While Rivers still treasures his Southern roots, Southern California has grown on the 35-year-old quarterback and his wife.

“With time, you feel part of the community,” Rivers said. “All but one of my children have been born out here. You begin over time to call it home. I’m very thankful, and always will be.”

Gates has long spent parts of his offseason in Los Angeles, so he has given his teammates plenty of tips on the sprawling metropolis. He also needs just one touchdown catch to become the NFL’s career leader in TDs by a tight end, and Gates is at peace with the fact that he’ll set the record and finish his career away from San Diego.

He still plans to visit several restaurants and other businesses around town to say a personal goodbye to the city that embraced him after he arrived as an undrafted college basketball player looking for a new life on the West Coast.

“It’s just one of those things where we want to take time out to say thank you to San Diego and to the fans that have supported us,” Gates said. “But at the same time, I’m excited to move to LA. I’m excited about the new change, and hopefully they’ll welcome us with open arms, embrace us, and we can win some games and win a championship.”