The NBA trade deadline has come and gone, and most of the best players on the buyout market have found new homes. 

That means the "they were so close" chatter associated with the Boston Celtics and top-shelf talent is once again alive and well. 

Boston's biggest trade deadline move came when it acquired Evan Fournier from Orlando for a pair of second-round picks.

In his ninth NBA season, the 2012 first-round pick of the Denver Nuggets was not among the top-tier players bandied about as being on the move. 

He wasn't even the top trade target (Nikola Vucevic) or the second-most sought-after target (Aaron Gordon) on the Magic roster.

Boston's inability to land the biggest names on the trade and buyout market speaks to the growing challenges it faces in remaining among the top teams in the East. 

Under eighth-year coach Brad Stevens, the Celtics have advanced to the Eastern Conference Finals in three of the last four seasons.

But this season, Boston is struggling to keep pace with the top teams in the East, such as Philadelphia, Brooklyn and Milwaukee, all of whom made trade deadline moves to bolster their status. 

Boston's fall from basketball grace lumps it into a quartet of back-of-the-pack playoff teams with Miami, Indiana and Chicago. 

"Winning is hard in this league," Danny Ainge, Boston's president of basketball operations, told B/R in an exclusive interview. "With the parity there is in the league and when you are not a superpower team, you have to work hard to play to beat anybody in this league. And that's been proven to us this year. Hopefully we can get that message. 

Ainge added: "It doesn't mean you're not going to bring your best effort every night. But we're a team that ... we don't have a lot of room for error. We're not like the 2008 [Celtics] team or the 1986 Celtics team or the 1966 Celtics team; sometimes you can play poorly and still win games. We have to play well to win on any given night. We just haven't."

So where do the Celtics go from here?

Rival executives believe Boston's status as an elite team in the East is in serious jeopardy of having run its course, pointing to the progress made by others in the conference, which has coincided with the Celtics' regression. 

Boston (23-24) hasn't had a below-.500 record at this stage of a season since the 2014-15 campaign, when a late surge catapulted the team into the postseason for the first time under Stevens (then in his second year in Boston). 

But the failures by Boston during the trade and buyout market season provide clues as to how the Celtics will try to climb their way back to the top of the East.

The Celtics have every intention of building their team of the future around All-Stars Jayson Tatum and Jaylen Brown, players that rival executives said were "untouchable" during this trade season. 

Ainge has indicated Boston will try to re-sign Fournier this offseason, a daunting task considering the team's salary-cap status next season.

Rival executives agree that for Boston to reemerge as a top-tier team in the NBA, it'll have to find a blockbuster deal akin to the kind of roster upheaval Celtics fans haven't seen since the Kevin Garnett trade from Minnesota in 2007. 

"I don't think they'll do something that dramatic," said an Eastern Conference executive. "But I would be very surprised if Danny doesn't make a big, bold move this summer."

Multiple league sources anticipate Washington's Bradley Beal will be a primary target for Boston this summer.

The 27-year-old Beal leads the NBA in scoring with 31.3 points per game while shooting an efficient 48.5 percent from the field. 

Beal and Tatum, both St. Louis natives, are very close and had a chance to be teammates during last month's All-Star Game.  

But rival executives indicate the Wizards have shown no desire to talk, let alone negotiate, with teams on a possible Beal trade, so Boston isn't holding its breath on getting a deal done. 

The Celtics were reluctant to include Brown or Tatum in any trade talks this past year, and that thinking has not changed, according to a league executive. 

Would Beal qualify? 

"Now you have something to talk about," replied the executive. 

But for Boston to put itself on the path toward basketball prominence, Ainge will have some tough decisions to make with his roster.  

While possible, it's highly unlikely Boston can pay Fournier what he would command as a free agent and keep the team's core group together. 

Tatum, Brown, Kemba Walker and Marcus Smart will earn about $104 million next season. Boston's guaranteed payroll for next season is around $132 million, which includes the second year of Tristan Thompson's mid-level exception.

Because of Thompson's MLE, the Celtics are hard-capped with a projected luxury-tax apron for the 2021-22 season of $143.1 million.

In other words, they'll need to make at least one major move on the trade front to create enough salary-cap space to re-sign Fournier. 

"With Danny, he could be bluffing; you just never really know for sure," said a second league executive when told about Boston's interest in re-signing Fournier. "But if he's serious about keeping Fournier, I can't see them doing so without trading a couple of guys."

Rival executives believe Boston will listen more intently than it has this past year for offers that involve Smart and Walker. 

Even if Boston is successful along those lines, it will need to fill out the back end of the roster with talent such as trade deadline acquisitions Luke Kornet and Moe Wagner. 

Will those moves be enough for a Celtics return to the short list of title contenders? 

That's unlikely. 

But rival executives remain convinced that if any GM can transform a good team like the Celtics into a great one overnight, it's Ainge. 

"Look at the track record," texted a Western Conference executive. "He got KG [Garnett] when nobody thought he could. DA [Ainge] flipped KG, PP [Paul Pierce] to BKN [Brooklyn] for the reboot. Danny'll get them back, just when you don't see it coming, like this summer. I hope I'm wrong, though."