49ers defense: Best and worst-case scenarios for 2025

Bleacher Report's Alex Ballentine identified cornerback as the San Francisco 49ers' biggest remaining defensive need, a point that sets the stage for his latest feature examining best- and worst-case scenarios for every NFL defense in the 2025 season.

The 49ers' roster underwent a significant overhaul this offseason, especially on defense. San Francisco revamped its defensive front to address last year's struggles against the run and inconsistent pass rush. The team used three of its 11 draft picks on defensive linemen, adding Mykel Williams, Alfred Collins, and CJ West.

If those rookies—and other additions—make an early impact, the 49ers will have a strong chance to bounce back from last season's disappointing 6-11 finish.

Best-case scenario: 49ers draft class delivers immediate impact

A best-case outcome for San Francisco would see the team's 2025 rookie class making meaningful contributions from day one. The departures of key defenders such as Dre Greenlaw, Talanoa Hufanga, Charvarius Ward, and Leonard Floyd leave big shoes to fill. The 49ers are counting on their newest additions to offset those losses.

"Getting big contributions out of first-round pick Mykel Williams, second-round pick Alfred Collins, and third-round pick Nick Martin would be a great start," Ballentine wrote.

Staying healthy will also be critical, as injuries were a significant factor in the team's struggles last season.

Ballentine added, "A healthy Nick Bosa and Fred Warner could help the Niners front rebound in a big way if the rookies are ready to play."

Worst-case scenario: Offseason departures prove too costly

The 49ers are relying on star players like Bosa and Warner to maintain their elite level of play. If either regresses, it could spell disaster for the defense. Fortunately, the team brought back Robert Saleh as defensive coordinator, which should help stabilize the unit.

However, Ballentine noted significant uncertainty surrounding San Francisco's secondary. In addition to Hufanga's departure, second-year safety Malik Mustapha is expected to miss the start of the season as he continues recovering from an ACL injury.

"That, combined with an unproven cornerback room, could lead to a leaky secondary," Ballentine warned.

The 49ers are projected to start Deommodore Lenoir and Renardo Green at cornerback, with the crucial third corner spot up for grabs during training camp. Players like Tre Brown and third-round pick Upton Stout will compete for playing time.

Bosa's performance will be crucial for San Francisco's hopes.

"He missed three games with a hip injury last season and his production has been on a downturn in each of the last two seasons," Ballentine commented.

He added, "If Bosa doesn't bounce back to being one of the league's best pass-rushers and Mykel Williams or Bryce Huff can't become a reliable No. 2, then the floor is actually pretty low in San Francisco."