Another school is on the verge of leaving the Pac-12 for the Big 12.

Sources told Yahoo Sports’ Ross Dellenger that Big 12 executives met Thursday to approve an application for Arizona to join the league. The Arizona Board of Regents was meeting on Thursday night with a formal approval to switch conferences expected to be finalized soon.

Arizona’s impending departure, the latest major shakeup in conference realignment in college athletics, comes on the heels of Colorado leaving the Pac-12 for the Big 12 last week. Like Colorado, Arizona’s defection to the Big 12 would be official for 2024.

Should the move come to fruition as expected, Arizona would become the fourth Pac-12 member to leave the conference in the past 13 months. Last July, UCLA and USC accepted invitations to the Big Ten, also effective 2024.

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With Arizona likely in the fold in addition to Colorado, the Big 12 would grow to 14 members. More could be on the way.

Sources told Dellenger that Arizona State and Utah are also expansion targets of the Big 12. However, talks with those schools have not progressed as quickly as Arizona, though the Sun Devils and Utes remain viable options to defect to the Big 12 with a decision expected in the coming days.

Though they are rivals, Arizona and ASU have long been linked at the hip. The two share a Board of Regents and were founding members of the old Western Athletic Conference before they left to turn the Pac-8 into the Pac-10 back in 1978. Forty-five years later, the two could make another conference move together.

What about Oregon and Washington?

Arizona’s expected departure would reduce the membership of the Pac-12 to just eight schools. If Arizona State and Utah follow suit, the league would be reduced to six members, including Oregon and Washington.

Oregon and Washington are seen as the two most valuable brands remaining in the Pac-12, and they could end up in the Big Ten. Yahoo Sports’ Dan Wetzel reported Thursday that the Big Ten is in wait-and-see mode with Oregon and Washington as its focus for possible expansion candidates with the Pac-12 on increasingly shaky ground.

On Thursday night, Dellenger reported that an offer from the Big Ten to Oregon and Washington would not be for a full share of its media rights revenue. The annual share would be in the range of $35 million to $40 million, per Dellenger. And with the cross-country travel associated with joining a conference primarily based in the Midwest, there has been a level of hesitancy to make the jump.

However, if Arizona State and Utah end up following Colorado and Arizona into the Big 12, Oregon and Washington may not be left with a better option.

Why are schools leaving the Pac-12?

The Pac-12 has been on shaky ground since the defections of USC and UCLA. The conference has been desperately attempting to land a new media rights deal for the past year. All the while, the Big 12 — which already extended its media rights deals with ESPN and Fox through 2031 — has aggressively pursued expansion candidates.

As of last week, the Pac-12’s presidents and chancellors had yet to be shown any financial figures regarding a new media rights deal by commissioner George Kliavkoff. The uncertainty proved to be too much for Colorado to withstand, and the school made the leap for the security of the Big 12.

The Pac-12’s presidents and chancellors were finally presented with the details of the media rights deal on Tuesday. The deal featured the streaming platform Apple as the primary rights holder with potential sub-licensing opportunities to linear television entities like ESPN and Fox.

When Colorado officially departed, school officials pointed to the visibility and reach provided by the Big 12’s TV deal as a preferable option. The Big 12’s deal would also provide a larger revenue share than the Pac-12’s.

The deal from Apple is still on the table and Pac-12 presidents are expected to meet Friday.