Duke coach Mike Krzyzewski will have back surgery Friday and miss an undetermined number of games, a source told CBS Sports early Monday.

Duke subsequently announced the development.

Krzyzewski's anticipated recovery time is four weeks.

Associate head coach Jeff Capel will coach in Krzyzewski's absence.

"Our medical team [has] worked tirelessly to help manage this issue for several weeks," Krzyzewski said. "Together, we have determined that surgery is the best course of action at this time. During my recovery process, the team will be in the capable hands of Coach Capel, Coach [Nate] James and Coach [Jon] Scheyer. As soon as the doctors clear me to do so, I look forward to returning and giving our team 100 percent of my energy and attention."

Here are five things to know:

1. Yes, this has happened before

If this news sounds familiar -- Coach K to miss games because of back surgery! -- it should. Because this will be the second time Krzyzewki has missed games because of back surgery. The first came in 1994-95. Krzyzewski only coached 12 games that season and the Blue Devils ended up missing the NCAA Tournament with a 13-18 record. Worth noting: They've made the NCAA Tournament every year since.

2. No, Coach K isn't stepping away because his team is 'struggling'

Some started suggesting, just as soon as the news was reported, that this is little more than Krzyzewski bailing on a season not going well, which is an absurd opinion on multiple levels. First and foremost, it discounts the pain this soon-to-be-70-year-old is experiencing. What I'm told is that Krzyzewski knew he couldn't coach another three months in this condition. So he opted for surgery now so that he can hopefully return in early February and thus in plenty of time for the NCAA Tournament. Simple as that. Beyond that, Duke isn't "struggling." In fact, the season is going remarkably well, all things considered. The Blue Devils are 12-2, ranked in everybody's top 10 and still the favorite in Las Vegas to win the 2017 NCAA Tournament despite the fact that the three most heralded freshmen (Harry Giles, Jayson Tatum and Marques Bolden) have each missed time with injuries, and the top returning player (Grayson Allen) is indefinitely suspended. All "struggling" teams should be so lucky, right?

3. This further complicates the Allen situation

Allen missed Saturday's loss at Virginia Tech and remains indefinitely suspended because of a third tripping incident inside of a year, and now Krzyzewski won't be around on a day-to-day basis to evaluate him. So is the date on which Allen returns still Krzyzewski's call to make? Or is that now up to Capel? There's no clear answer to either question, at this point. But it's a situation worth following.

4. What a big opportunity for Capel

It's never been clear who will replace Krzyzewski when he eventually retires. But Capel is on the short list of obvious candidates. So this could be interpreted as a de facto audition. Assuming Krzyzewski actually returns exactly four weeks after surgery, Capel will coach seven Duke games -- specifically games against Boston College, Florida State, Louisville, Miami, NC State, Wake Forest and Notre Dame. A good run could lead to a life-altering opportunity for the former VCU and Oklahoma head coach. But a bad one might cost him as much. So the stakes are high.

5. The selection committee will monitor this closely

There's a good chance Duke will be fine under Capel considering the Blue Devils can still overwhelm, from a talent perspective, most opponents. But if they struggle for some reason, and then flourish in Krzyzewski's return, the NCAA Tournament selection committee can and will consider that while seeding Duke. So keep that in mind if the next four weeks don't go smoothly for the preseason No. 1 team. Because the people in charge of the 68-school bracket absolutely will.