ESPN's Adam Schefter reported the news Sunday.
Gates has carved out one of the best careers for any pass-catcher in NFL history. He ranks sixth all-time with 114 touchdown receptions, 20th in total receptions and 30th in receiving yards. He played in eight consecutive Pro Bowls (2004 to 2011) and was a first-team All-Pro in three straight seasons (2004 to 2006).
Prior to the 2015 season, which was his last under his previous contract with the Chargers, Gates told Michael Gehlken of the San Diego Union-Tribune he couldn't make a definitive statement about when he would walk away from the game:
"As you get older, people say things. They make speculations about where you're going, about how much you have in the tank. To me, it's all about how I feel as a person, how my body feels physically and mentally. As of right now, I feel great physically. I'm in a great place mentally. So, we'll see how it goes. I have no expectations for how long I'll play or if this is my last year."
With the Chargers giving second-year tight end Hunter Henry the keys to the starting job at tight end, Gates' role in the offense was significantly diminished in 2017. His 316 yards were his fewest in a single season, and his 30 receptions marked his lowest total since he was a rookie in 2003.
Because the Chargers have given Gates a reduced role, his body isn't being as taxed as it was when he was starting every week. The team is still good enough to compete for a playoff spot in the AFC next season, so he has one more chance to cap off his historic career with a Super Bowl title.
The Chargers emerged as a likely landing spot for Gates when Hunter Henry suffered a torn ACL on the first day of organized team activities on May 22. He finished third on the team with 45 receptions, 579 receiving yards and tied for second with four touchdowns.
Earlier in the offseason, Schefter reported the Chargers told the 38-year-old they were not going to bring him back.
Given his age, Gates isn't going to be the player he was at his peak when he was the best tight end in the NFL. He does have a familiarity with the offense and built-in rapport with quarterback Philip Rivers that will allow him to be successful for a Chargers team with playoff aspirations coming off a 9-7 season.