As Ryan Day looks to hire his fourth defensive coordinator in seven seasons, here are potential candidates to replace Jim Knowles.

Knowles would fill the void on Penn State’s staff left by Tom Allen, who accepted the same position with Clemson earlier this month.

Knowles, a Philadelphia native with strong ties to the Northeast, transformed the Buckeyes' defense during an impressive three-year stint. Ohio State ranked top three in total defense each of the past two seasons and led the nation by holding opponents to 254.6 yards per game and 4.2 yards per play during a historic campaign.

Here are three potential options who could fill the Ohio State Buckeyes' defensive coordinator vacancy in 2025.

According to The Action Network's Brett McMurphy, Knowles was asked by school not to attend Buckeyes’ national title celebration while he deliberated his coaching options. Not long after the rally concluded, it was announced that Knowles was signing a contract to become the next DC for the Penn State Nittany Lions, a major Big Ten rival.

Just as Ohio State was celebrating its national championship victory at Ohio Stadium on Sunday, news broke that Jim Knowles was heading to Penn State.

However, Knowles wasn’t in attendance. About an hour later, reports surfaced that Knowles is leaving Ohio State to serve as Penn State’s next defensive coordinator. The move leaves Day searching for a replacement. Here’s who he might consider as he enters his seventh season as the Buckeyes' head coach.

Penn State has lured Tom Knowles away from Ohio State. The Nittany Lions have hired Knowles to serve as their defensive coordinator.

As Ohio State’s celebration tour for the school’s ninth national title continues, some of the Buckeyes’ key defensive players are grappling with the departure of their defensive coordinator. Jim Knowles decided to leave Columbus for Big Ten rival Penn State after three years at Ohio State,

Jim Knowles is expected to take the same position at Penn State, as first reported by Yahoo Sports' Ross Dellenger. The two sides are finalizing a three-year deal reportedly worth $3.1 million per season, making him the first college football coordinator to earn an annual salary of at least $3 million.

Ohio State’s defensive coordinator is celebrating winning a national championship with a new contract — from one of their rivals.