Joyner had previously signed the franchise tag and will play next season on a one-year, $11.3 million deal, but the two sides couldn't settle on a longer contract.
Schefter reported Sunday "the two sides continue talking," but the lack of a new deal isn't much of a surprise.
The 27-year-old is coming off the best season of his career, starting all 12 games he played after transitioning from cornerback to safety. Despite missing four games with a hamstring injury, he ranked sixth on the team with 49 tackles and added three interceptions with one returned 104 yards for a touchdown.
While Joyner had played 40 games in his first three years in the NFL, it was mostly off the bench in nickel and dime packages and usually closer to the line of scrimmage.
He showed last season he could be an elite defender against the pass—Pro Football Focus rated him as the third-best safety in the NFL in 2017—but he now has to prove that it wasn't a fluke.
Although Joyner will earn a significant raise from the $1.1 million he made in 2017, per Spotrac, it appears the Rams want to see more of him at safety before committing to a long-term deal.
With Aaron Donald also expecting a high-priced deal, Los Angeles could be forced to spend big to keep their best players in 2019 and beyond.