Darren Yamashita-USA TODAY Sports

As Super Bowl 58 approaches, San Francisco 49ers fans harbor concerns about the team's defensive performances in the playoffs. The 49ers clinched two dramatic come-from-behind victories, including overcoming a 17-point deficit against the Detroit Lions in the NFC Championship Game.

The team acknowledges the issue, and coaches hope they have sufficiently addressed it ahead of Sunday's showdown with the AFC champion Kansas City Chiefs.

"Effort's a non-negotiable," general manager John Lynch emphasized last week. "I mean, that's one of our core values, and I believe that in my heart of hearts. We've got four Hall of Famers that represent the defense I played in at Tampa, and if you ask every one of us that played on that defense, 'What was our calling card?' It starts with effort, that being a non-negotiable."

Lynch added, "It's been addressed, and I'd be real surprised if I saw [it during the Super Bowl]."

Defensive end Chase Young, acquired via a midseason trade, understands there is room for improvement.

"We know we have to do better," Young told NBC Sports Bay Area on Monday night. "We have to do more. Can't have that. I can't have that. And everybody on the team knows that we can't have that. So, we're going to do our best to make sure it never happens again."

When asked if the criticism regarding a lack of effort is something he takes personally, Young responded, "Yeah, definitely. We definitely can't have that on the field, especially when you want to be a top defense in this league."

The two playoff games revealed that the Niners can win these tough matches. The team feels battle-tested and ready for whatever challenges the Chiefs might present in Super Bowl 58.

"Definitely knowing that, if we get in a tight spot, that we can buckle down and get it done," Young said. "But I feel like these are the type of games where you can't get down like that. So it's our job to start fast and do our job from the start."

Last week, defensive coordinator Steve Wilks discussed his unit's effort in the recent comeback victories.

"Collectively, as a team, I can tell you, as a defense, it's unacceptable, all right?" Wilks declared. "We talked about that. I wish I could tell these guys on play four, on play 27, this is what's going to happen. You don't know. So we've got to make sure that we play every down as if it's going to be the difference in the ball game.

"And you could see on those particular plays, it wasn't to our standard. Those guys understand and know that, and quite honestly, it was embarrassing."

The 49ers and Chiefs kick off from Allegiant Stadium on Sunday at 3:30 p.m. PT.

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