Brooklyn Nets head coach Steve Nash concedes his side must have urgency to arrest their slide after Thursday's 129-106 loss to the Boston Celtics left them with a 31-29 record.

The Nets were billed as title contenders earlier this season but have endured a tough midseason period, winning only two of their past 15 games with Kevin Durant out injured, Kyrie Irving unavailable for home games and James Harden traded out.

Harden swapped places with Ben Simmons from the Philadelphia 76ers, with the new acquisition still yet to debut as he re-conditions having not played this season.

Nash admitted having a healthy roster would go a long way to fixing his side's issues but conceded they needed urgency as their season slips away.

"We understand the situation we're in. We know there's urgency," Nash said at the post-game news conference.

"We're not going to have half a season to figure this thing out. We're up against the clock.

"Our guys have been great. There's a lot of pressure and circumstances that make it difficult as you're dropping in the standings but their spirit has been outstanding.

"That's the spirit of taking it day-by-day game-by-game trying to improve. At the same time, we recognise the situation we're in."

Jayson Tatum starred for the in-form Celtics with 30 points and seven rebounds, while the Nets' best were Seth Curry (22 points and seven rebounds), Bruce Brown Jr (15 points, seven rebounds and five assists) and Kessler Edwards (13 points and five rebounds) off the bench.

Nash was pressed on ways to fix their struggles without their key players, with no timeframes on Durant and Simmons' availability but he reverted to a healthy roster.

"That's number one, two, three and four really," Nash said. "We could've played better tonight, but we can play better on nights when we have everybody too.

"In this league, you flip it, take four of the Celtics starters out, it's a different look."