NBA coaching vacancies in Portland, Boston, Indiana and Orlando—and the potential for at least one more in Milwaukee—have driven much of the conversation among league personnel over the past week.

For those ongoing searches, it's expected that each of the Blazers, Celtics, Pacers and Magic will publicly conduct lengthy, wide-ranging interviews.

Portland general manager Neil Olshey, for example, told reporters his front office plans to meet with 20 to 25 candidates. However, league sources have long expected and continue to pinpoint Clippers assistant coach and former Finals MVP Chauncey Billups as the likely next head coach of Damian Lillard and the Trail Blazers.

The Celtics have already requested an interview with Billups too, as ESPN's Adrian Wojnarowski first reported. Billups was one of five assistant coaches Boston contacted for its position, along with Darvin Ham and Charles Lee (Bucks), Ime Udoka (Nets) and Jamahl Mosley (Mavericks). All are highly regarded young coaches who are said to relate well with players—something that appears to be a preference for Boston, as well as having playing experience in the NBA. Of that list, only Mosley and Lee did not reach the league as players.

Team personnel contacted by B/R maintain that hiring a Black candidate is another top priority for the Celtics. If Boston can also land someone who has previous head coaching experience, that person would further meet the Celtics' criteria, sources said.

With that, Nate McMillan is an under-the-radar contender to become Boston's 18th head coach in franchise history. All indications are that Atlanta will remove the interim tag from McMillan's title and offer an extension, sources said. Yet until that deal is agreed upon, there remains a potential for McMillan to benefit from his successful stint guiding the Hawks through this postseason and test the market elsewhere.

Meanwhile, McMillan's former employer, the Pacers, have set out to find their second head coach since dismissing him at the end of the 2019-20 campaign. And in the days before Indiana announced it had parted ways with Nate Bjorkgren, league sources increasingly linked former Blazers head coach Terry Stotts as a leading candidate for the Pacers job.

A similar pressure exists in Portland, Boston and Indiana to find a coach capable of leading a deeper playoff run. And the Pacers, sources said, are the franchise that seems most concerned with hiring a candidate with previous NBA head coaching experience following the failed one-year tenure of Bjorkgren.

Nets assistant Mike D'Antoni has been connected to Indiana for some time in his own right. Additionally, after Steve Clifford and the Magic parted ways, the two-time NBA head coach is expected to be considered for the Pacers' job.

Clifford had one year remaining on his contract with the Magic, and after being hired to help lead a perennial playoff outfit in Orlando, it's believed the veteran coach has an interest in joining another team with postseason aspirations, not a franchise that expects to undergo a several-year rebuild.

Meanwhile, Orlando's search appears to be the most fluid, and a host of names continue to be rumored as candidates.

Momentum had seemed to stall for Jason Kidd after he was originally linked to Boston and Lillard went on record vouching for him in Portland, but the Lakers assistant's name has surfaced more and more in conversations about Orlando's opening. League sources have cited a connection to Magic general manager John Hammond, who hired Kidd to coach Milwaukee back in 2014.

Clippers assistant Kenny Atkinson has been the name most often connected to the Magic. The former Nets head coach was a finalist for the Pelicans' opening last offseason and still holds a reputation around the league for being a skilled player developer from his days leading Brooklyn back to the playoffs.

Or perhaps the Magic go with a first-time head coach like Udoka, who league sources have strongly linked to this opening as well. Although there is a belief that Udoka has a greater interest in joining Boston. 

Jarron Collins, one of three player development-leaning coaches dismissed as part of a shakeup with Golden State's staff, has already had conversations with Orlando too, sources said.

With an emphasis to hire a younger, player development-focused candidate, other assistants like Ham and Lee would also make plenty of sense with the Magic too. Choosing Sixers assistant Sam Cassell would be popular among Orlando's group of returning players, sources said.

Elsewhere in the Eastern Conference, even as the Bucks have matched the Nets 2-2 in their semifinals matchup, there continues to be an expectation among league sources that Milwaukee will move on from Mike Budenholzer after three seasons at the helm if the Bucks fall short of the Finals. If that scenario unfolds, it would open perhaps the most coveted head coaching vacancy in the NBA.

It certainly makes sense that D'Antoni appears to have shown interest in leading the Bucks, sources said. Including Portland's situation, it is said D'Antoni is motivated to find another head coaching role for the 2021-22 season. Mavericks head coach Rick Carlisle is another longtime coach who's been rumored to have an eye on Milwaukee's potential opening.

Dallas owner Mark Cuban publicly backed Carlisle as the Mavericks head coach following their series-ending loss to the Clippers, but that would not prevent the Bucks from requesting permission to speak with him. Although Milwaukee assistants Ham and Lee would be expected to garner strong consideration as well, sources with knowledge of the situation told B/R.

Ham in particular is said to be a favorite of Bucks players, as it's believed Milwaukee's roster could benefit more from a change at the top rather than an entire transition away from Budenholzer's staff. If the Bucks do look to hire a candidate from outside their facility, current Olimpia Milano head coach and former Spurs assistant Ettore Messina is another name to keep an eye on, sources said.

Some final notes: Charlotte and head coach James Borrego are expected to come to terms on a new contract extension, sources said. It appears Scott Brooks will stay on as the Wizards head coach after leading Washington to the eighth seed and following impassioned pleas of support from Russell Westbrook. In Minnesota, head coach Chris Finch has begun interviewing candidates to round out his new Timberwolves staff. 

Jake Fischer covers the NBA for Bleacher Report and is the author of Built to Lose: How the NBA's Tanking Era Changed the League Forever.