The Brooklyn Nets started the trade season in January when former MVP James Harden was acquired in a four-team deal. The Harden addition strengthens what many had already considered a championship contender in Brooklyn.

What else should we expect between now and the 2021 NBA trade deadline on March 25?

The selling and buying market could be dormant because the play-in tournament adds four postseason teams who would otherwise be sellers. Additionally many contenders lack draft assets to send out in a trade because of moves they've made in recent years.

Here, we break down what to watch for all 30 teams: what kind of moves they can make, what we're hearing, front-office trade histories and trade restrictions of note.

Atlanta Hawks

What to watch: John Collins, Bogdan Bogdanovic and Kris Dunn

The Hawks are currently in 11th in the East, but just a game out of 8th (and two games back of the 4th-place Pacers), and should be in contention for at least a play-in spot this May.

Atlanta's offseason spending spree ($160M on free agents this past fall) and competing for a playoff spot should keep Collins off the board, despite restricted free agency looming in the offseason.

If trade discussions do emerge, it will be a result of Atlanta not being comfortable giving Collins a max-level contract this offseason, especially with Trae Young being eligible to sign an extension this summer.

Collins ranks as the No. 1 power forward in free agency, and teams like Dallas, Miami and New York are well positioned to sign him to an offer sheet starting at $28 million for the first season.

Atlanta's big deadline "acquisitions" will likely be the return of free-agent signings Bogdan Bogdanovic and Kris Dunn from injury. Dunn (ankle) has not appeared in a game this season, and Bogdanovic (knee) has seen action in nine.

Front-office deadline history: GM Travis Schlenk has made nine deadline deals during his tenure, including the four-team, 12-player trade in 2020 to acquire Clint Capela. The Hawks also received $3 million, a future second-rounder and Dewayne Dedmon in three separate trades last February.

Restrictions/notes

The Hawks have a 2022 first-round pick from Oklahoma City that is top-14-protected. The pick turns into a 2024 and 2025 second if not conveyed next year.

Bogdan Bogdanovic has a 15% trade bonus in his contract.

The Hawks received $750K in the Danilo Gallinari trade and can take back up to $4.86 million.

Boston Celtics

What to watch: The $28.5 million trade exception

Boston is not facing a use-it-or-lose-it scenario with the $28.5 million exception created in the Gordon Hayward sign-and-trade with Charlotte. The exception doesn't expire until the fall, so Boston could use part of it now and the balance this offseason.

For example, the Celtics could trade for a player like the Rockets' P.J. Tucker or Kings' Nemanja Bjelica, remain under the luxury tax and have $20.6 million left to use in the offseason. Boston is currently $15.5 million below the luxury tax and $19.9 million below the hard cap.

Boston could target the Kings' Harrison Barnes or look for a reunion with Al Horford, but that would risk putting the Celtics into the luxury tax both now and next season. Also, because Horford's $27.5 million salary would put Boston over the hard cap line, the Celtics would need to shed $7.6 million in salary in a deal that brought him in.

One advantage the Celtics have is that there are no restrictions on trading their first-round pick this year or in any future year.

They also have their own second-round pick in 2021, 2022, 2025, 2026 and 2027, in addition to the Grizzlies' 2025 second-round pick.

The question is what is Boston willing to sacrifice to go from an average team to one that can compete with Brooklyn, Philadelphia and Milwaukee? Are the Celtics willing to go deep into the luxury tax not only this year but in future years and are they willing to trade first-round picks to improve the team?

We have seen over the years that championship contending teams have all made high risk moves when it comes to their roster.

Recent examples include Golden State and Cleveland spending more than $200 million toward the luxury tax, Toronto acquiring Kawhi Leonard in 2018, the Anthony Davis trade that stripped the Lakers of their young players and draft picks and, most recently, the Nets trading away all their future assets in the James Harden trade.

Front-office deadline history: One of the NBA's longest-tenured executives, Danny Ainge is not known for making changes to the roster during the season. The only two in-season deals Boston has made since 2015 are acquiring Isaiah Thomas from the Suns and dumping the contract of Jabari Bird in 2019.

Restrictions/notes

The Celtics are $19.9 million below the hard cap and $15.5 million below the tax.

Jayson Tatum has a poison pill restriction in his contract.

Kemba Walker has a 15% trade bonus. The bonus would be voided because it exceeds the maximum salary in 2020-21.

In addition to the $28.5 million trade exception, Boston also has $4.8 million and $2.6 million exceptions.

The Celtics cannot reacquire Hayward, Enes Kanter and Vincent Poirier.

Brooklyn Nets

What to watch: The $5.7 million disabled player exception and Spencer Dinwiddie

Despite the inability to trade a first-round pick in any season, the cupboard is not completely bare for the Nets.

Brooklyn has a $5.7 million disabled player exception (created with the injury to Dinwiddie) available to acquire a player who is in the last year of his contract. The exception cannot be split and will expire after it is used once. The exception cannot be combined with another player on the Nets' roster to trade for a player with a higher salary (for example, pairing Landry Shamet with the exception to create room for someone making $7.7 million). It will also extinguish if Dinwiddie is traded from now until the March 25 deadline.

To use the exception, the Nets would likely have to attach one of the many second-round picks they possess. Brooklyn has picks from the Hawks and Suns in 2021, the Pacers in 2023 and the Warriors in 2025 in addition to its own second-round picks in 2022, 2024, 2026 and 2027.

Because there is a lack of big men on the roster, some names to keep an eye include Khem Birch (Orlando), JaVale McGee (Cleveland), Ed Davis(Minnesota), Mike Muscala (Oklahoma City) and Hassan Whiteside(Sacramento).

With regard to Dinwiddie, despite being in the last year of his contract (he has a player option in 2021-22) and out for the season, the guard has value because the acquiring team would retain his Bird rights, allowing it to exceed the cap to re-sign him as a free agent.

With 73% of the teams projected not to have cap space this summer, Brooklyn could also hold on to him past the trade deadline and explore sign-and-trade options in the offseason.

Front-office deadline history: Nets GM Sean Marks has made 21 trades since taking over in 2016, with three at the deadline. In 2019, the Nets took back Greg Monroe and a 2021 second-round pick in a move that helped save Toronto $4 million. The pick was sent to Detroit this past November for Bruce Brown.

Restrictions/notes

The Nets have 12 players on guaranteed contracts and the flexibility to open up three roster spots.

Brooklyn is $31.8 million over the luxury tax.

In the James Harden trade, $2.6 million was sent to the Pacers. As a result, Brooklyn has $3 million in cash to send out in a trade.

Kyrie Irving and Kevin Durant both have a 15% trade bonus. The bonus would be voided because it exceeds the maximum salary in 2020-21.

Brooklyn is not allowed to trade a first-round pick in any year.

Tyler Johnson has a one-year Bird restriction and can veto any trade.

The Nets cannot reacquire Jarrett Allen, Rodions Kurucs, Caris LeVert and Taurean Prince.