The hosts of ESPN’s “Sunday NFL Countdown” pregame show didn’t mince words when describing how the San Francisco 49ers defense has struggled this year. In a discussion previewing Sunday’s Super Bowl rematch with the Kansas City Chiefs, ESPN insider Adam Schefter kicked off a discussion about the 49ers defense by dropping a nugget of reporting from his conversations with other teams.

“This defense is not performing at the same level that it was in recent years,” Schefter said. “They lost Arik Armstead, they lost Javon Kinlaw, they haven’t gotten the same production that they’ve needed. When you speak to other teams around the league, it feels to them like something is missing from the 49ers’ defensive line. It’s not the same defensive line.

“It’s a defense that’s blown leads on the road against the Rams, it’s blown leads at home against the Arizona Cardinals, they haven’t closed teams out — like the Guardians in baseball. The defense, as great as it’s been, it’s been a little off.

Whether Kinlaw leaving for the Jets is helping or hurting the 49ers is up to debate, but Schefter’s co-hosts on the ESPN show agreed with his assessment — and that’s even with Nick Bosa on the roster. Tedy Bruschi pointed out that the 49ers made an aggressive move at the trade deadline last season to acquire Chase Young (who also left to sign with New Orleans), with the aim of helping that defensive line.

“That D-line, that’s what predicates this defense,” Bruschi said. “And if they’re not playing well, Schefty, you’re right, that’s tough.”

Rex Ryan also agreed, quickly chiming in: “That’s what happens when you rely on just your front four to get pressure on the quarterback.” Ryan also brought up how Patrick Mahomes has three double-digit comebacks in a row against the Niners to highlight the 49ers’ struggles, especially when compared to the Chiefs and their defensive coordinator (and apparent 49ers offseason target) Steve Spagnuolo.

“That’s [what happens] when your system is just predicated on four guys winning,” Ryan said. “The thing I love about Kansas City is, with Spags, you don’t know what you’re going to get, where it’s coming from.”

ESPN’s hosts see Sunday as a key game for the 49ers because of their winless record against Mahomes, with Bruschi adding that the Niners’ belief that they can beat Kansas City is “hanging on by a thread” at this point.

“They can’t get revenge for any Super Bowl loss,” Bruschi said. “Because it’s not like this is boxing, where there’s a belt and you can just knock a guy out and you get his belt. That championship can never be won back, no. But you can get some sort of relief that, ‘Man, maybe we can beat these guys and we showed it. It was the regular season, yes, but at least we showed we can possibly beat them.’”

The 49ers will get that chance on Sunday, with kickoff set for 1:25 p.m. on Fox.