SANTA CLARA, Calif. -- With the NFL's salary cap expected to drop and the San Francisco 49ers unlikely to have much space to re-sign their many pending free agents, cornerback Richard Sherman believes this could be his third and final season with the team.

In fact, Sherman said Thursday it would take something out of the ordinary for him to return to a team that is slated to have about 40 players reach some sort of free agency, including left tackle Trent Williams, and is expected to make signing star linebacker Fred Warner to a lucrative extension one of its top offseason priorities.

"If there's some miracle that happens, then sure there's an opening," Sherman said. "But there's 40 free agents and they'll probably have $30 million or less in cap and they have got to bring back Trent, who costs over $20 million. They have to pay Fred, who costs $18 million-plus a year. So anybody who knows the situation understands that."

Sherman, who represents himself in contract negotiations, said his pessimism about remaining with the Niners is tied both to his direct knowledge of what could happen with the salary cap from his work with the NFL Players Association and his conversations with team management.

Those economic and roster realities undoubtedly figure to make it difficult to keep Sherman, but that doesn't mean the Niners are eager to lose him. Coach Kyle Shanahan said last week that he would like to find a way to keep Sherman with the team.

"Sherm's a guy that I know personally, and I know [general manager] John [Lynch] feels the same [that] we want on our team at all times," Shanahan said. "Sherm's a guy that, when he does get older and he does descend, he's such a good football player, he finds a way. I understand his contract issue this year. I understand there's a number of guys on our team with that this year, but whoever can help us win football games, our guys are trying to figure out how to bring [them] back, especially guys who do it the right way.

"Sherm is as good as anyone in those categories. Now, there's lots of stuff that go into it at the end of the year and how we're going to balance all this out and wait to figure out what the salary cap is and stuff with what happens, but I know Sherm's time here, he's been everything we've hoped and more. And I really hope that these next whatever games we have left, I really hope that's not the end of it."

In his 10th NFL season, Sherman, 32, returned in Week 12 against the Los Angeles Rams from a calf injury that had kept him out since Week 1. Before this season, Sherman had served as not only a stabilizing locker room presence but returned to form in 2019, when he earned second-team All-Pro and Pro Bowl honors as the 49ers won the NFC championship.

Sherman signed a three-year, $27.15 million contract with incentives making it worth more than $30 million in 2018 after spending seven seasons with the Seattle Seahawks.