The Celtics did not realize then how the trade would shape their immediate future, with Thomas emerging as a two-time All-Star who is now chasing a scoring title. But the general lesson learned was that even seemingly tranquil deadline periods can turn hectic in a hurry.

Over time, the talks seemed to fizzle, leading both sides to believe it would be best to pursue other options. But then negotiations improbably reignited in the final hour. And just minutes before the deadline, they agreed on a deal that would send Thomas to Boston in exchange for reserve guard Marcus Thornton and a first-round pick.

A few weeks before the NBA trade deadline in 2015, the Celtics and Suns began to have exploratory conversations about a deal that would send point guard Isaiah Thomas to Boston.


This year, the Celtics have been in numerous discussions for weeks, according to league sources. All-Star weekend was mostly calm, but activity is expected to pick up as Thursday’s deadline draws closer.

When DeMarcus Cousins was traded by the Kings to the Pelicans this week, many believed that removed a potential target from Boston’s wish list. But league sources said the Celtics never engaged in trade discussions with the Kings about Cousins, and that they never even had interest in him.

The Celtics have made no secret of their desire to add a transcendent talent, and the reality is that there may be no such players available. They have had discussions in the past with the Bulls about All-Star forward Jimmy Butler but it is unclear whether the sides will re-engage in meaningful talks this week.

Pacers wing Paul George is the other big name that has often been linked to the Celtics. But a league source said the Pacers still have given no indication that they would consider dealing the All-Star.


The 76ers, meanwhile, have been quite transparent about their intentions to trade their second-year big man, Jahlil Okafor, but the source said Okafor is not on the Celtics’ radar.

All indications are that Boston’s potential seismic strike is more likely to come in the summer. But that does not mean the trade deadline will pass with no movement.

The Celtics have identified a small group of role players they could have interest in, and Suns forward P.J. Tucker is among them. But Boston will not go overboard or hinder its flexibility chasing these deals, and it has no plans to relinquish a first-round pick for a player like Tucker, who would simply offer assistance off the bench, a source said.

The Celtics have been rattled by injuries this season, but the readiness of the reserves has been an important silver lining amid all the bumps and bruises. Jaylen Brown, James Young, Gerald Green, and Terry Rozier have all stepped into important roles when called upon recently. And their strong, reliable play has reduced some of the urgency to give up assets for bench help now.

The Celtics are in an unusual position because they are a rare top-tier team that is also in line to potentially receive the No. 1 overall pick in the draft. They have the right to swap first-round choices with the Brooklyn Nets, who currently own the worst record in the NBA and are all but guaranteed to remain there.


When teams have contacted the Celtics about potential trades, the teams “always start” with that Nets pick, a source said. This is considered one of the most talented drafts in years, but the Celtics have made it clear that the pick is not untouchable.

For now, the Celtics would just like to have a sustained stretch in which they are completely healthy. There is cautious optimism that Avery Bradley (Achilles’) and Brown (hip flexor) will both return to face the Raptors Friday night. Within the organization, there is a belief that chasing the Cavaliers with this team, then moving forward with free-agent flexibility and a top draft pick in the summer, might be the wisest approach.

But if there is a sudden opportunity to make a big splash, the Celtics will not be afraid to test the waters.

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach