The Pac-12 has decided to go to a conference-only model for fall sports, following the lead of the Big Ten, which announced the same move on Thursday.

It's the latest setback during a college football offseason that has been upended by the coronavirus pandemic, and is almost assuredly not the last domino to fall as conferences attempt to cobble together a season.

While so much about the season remains unknown, here's what we know now that 40% of the Power 5 has moved to conference-only football schedules.

Are the ACC, Big 12 and SEC going to follow suit? If so, when?

It seems to be trending that way.

"Over the last few months, our conference has prepared numerous scenarios related to the fall athletics season," ACC commissioner John Swofford said. "The league membership and our medical advisory group will make every effort to be as prepared as possible during these unprecedented times, and we anticipate a decision by our board of directors in late July."

One ACC source said it is "very likely" the ACC is headed to a conference-only season but reiterated it is a week-to-week discussion that continues to evolve.

Big 12 commissioner Bob Bowlsby told ESPN on Friday that his conference is on the same timeline as the ACC, pointing toward a decision by late July.

The SEC will discuss its options during a meeting Monday with athletic directors and league officials that was scheduled before the Big Ten's decision.

SEC commissioner Greg Sankey said in a statement last week there should be more clarity about the season by late July, and issued a similar statement to ESPN on Friday, referencing "the coming weeks."

"The Southeastern Conference will continue to meet regularly with our campus leaders in the coming weeks, guided by medical advisors, to make the important decisions necessary to determine the best path forward related to the SEC fall sports," the statement read. "We recognize the challenges ahead and know the well-being of our student-athletes, coaches, staff and fans must remain at the forefront of those decisions."

How likely is a spring season at this point?

More likely than a couple of weeks ago, but it's still viewed as a last resort by many. A spring season raises a new batch of questions regarding player safety -- can they physically handle two seasons, even shortened ones, in one calendar year? -- the NFL draft and uncertainty about the state of the virus and a vaccine by the new year.

Spring football is an option, Duke coach David Cutcliffe said on Friday, "when it's the only option left," echoing sentiments by Penn State AD Sandy Barbour and Bowlsby, who both called it a "last resort."

American Athletic Conference commissioner Mike Aresco went even further.

"We don't have much of an appetite for spring football ... we're not confident that spring football, if we don't play in the fall, will even happen," he said. "Especially if there's no vaccine. And we're not really sure that it's not going to compromise part of the 2021 season if you're playing in the spring. Also, if you have to practice in the middle of the winter to get ready for your spring football, you're practicing indoors, are you going to spread the virus more easily in that scenario? These are rational questions that have to be answered."

Not everyone is so skeptical, though.

"I think the people who say it's not [an option], in my opinion, just don't want to think about it," Oklahoma coach Lincoln Riley said earlier this month. "I just think it would be wrong of us to take any potential option off the table right now. I think it'd be very difficult to say the spring is not a potential option. I, for one, think it's very doable. ...

"It'd probably be a conference season and postseason only. We've seen often teams go in and play well into January in the College Football Playoff and start spring practice at some point in February, and nobody says a word about that. You'd have to give players plenty of time off to get their bodies back in the summer. Maybe a little later start back the next fall."

What does conference-only play mean for Notre Dame?
The Fighting Irish have now lost three marquee games -- Wisconsin, USC and Stanford. The most likely and expected scenario remains for Notre Dame athletic director Jack Swarbrick and ACC commissioner Swofford to extend their partnership and have the Irish fill the rest of their schedule with ACC games. Notre Dame is already set to play six ACC opponents.

What about other teams scheduled to play the Big Ten or Pac-12 in nonconference?
To be determined. After the Big Ten and Pac-12 announcements, conferences and teams affected put out statements that were similar to this one from Mountain West commissioner Craig Thompson:

"We were aware of this possibility and will continue to evaluate the appropriate decisions and the proper timing going forward. The safety, health, and wellness of our student-athletes, coaches, staff members and campuses remain our top priority."

After Alabama's showcase opener against USC was canceled, Crimson Tide AD Greg Byrne said "we will do our best to adjust."

Speaking of marquee games, which high-profile ones have been canceled so far?

Oregon has lost two fascinating ones, first with FCS power North Dakota State and its NFL draft darling QB Trey Lance. Then the Ducks were slated to host Ohio State in Week 2.

USC loses games with Alabama and Notre Dame, and the Irish also will miss playing Wisconsin at Lambeau Field in Green Bay. Jim Harbaugh and Michigan were scheduled to open the season at Washington, and the Utah-BYU rivalry game is also off for the year. BYU could lose as many as six games off of its schedule if the rest of the Power 5 leagues follow suit.

What will the season look like for the Pac-12 and Big Ten?

For the Pac-12, it will be delayed.

One of the reasons the conference decided to push back the start of the football season was a concern that UCLA and USC would not be ready to play in early September because of coronavirus cases in the Los Angeles area, sources told ESPN.

Big Ten officials, meanwhile, are still considering the possibility of moving its division games to the front of the schedule, in case the season is interrupted by the coronavirus. That way, it might still be able to determine a championship through division winning percentage in spite of an incomplete season.

Ohio State athletic director Gene Smith is still hoping for a full, 10-game conference schedule.

"I'm hopeful that that's where we end up next week in locking that down," he said. "We've talked about that, and that's our preference."

"We have not delved deep into those details yet," Smith added. "I anticipate next week we'll get into the details of how our schedules will work."

Smith also said if teams are able to play in September but something happens later in the month or in October, "we can hit the pause button and provide a window of opportunity for our student-athletes not to be put at risk. We can move games. ... There's a flexibility, I can't say that enough, that's significant."

Get used to it. If there is going to be a season this year, every option needs to be on the table.

What does this mean for the College Football Playoff and bowl games?

CFP executive director Bill Hancock has told ESPN that the playoff will be ready for "whatever comes down." As for the overall bowl system, the immediate impact is unknown. It depends in part on what the other conferences decide. If the other Power 5 conferences follow the Big Ten's lead and play only conference games, overall league depth will be the most significant factor in the eyes of the CFP selection committee. Teams from top-heavy leagues and divisions might have more trouble since they won't have the opportunity to secure big nonconference victories, particularly if they stumble in conference play.