Steve Nash was "optimistic" NBA MVP candidate James Harden did not suffer a long-term setback as the Brooklyn Nets went top of the Eastern Conference with a win that gave Kyrie Irving cause for concern.

Playing the Houston Rockets, his former team, Harden played only 27 minutes - registering 17 points, eight rebounds and six assists - before succumbing to hamstring tightness.

Irving led the way in his stead, as 31 points and a season-high 12 assists secured a 120-108 victory that moved the Nets ahead of the Philadelphia 76ers at 33-15 in the East.

But with Kevin Durant still out, having played just 19 games this season, Harden's injury prompted some concern.

The nine-time All-Star has averaged 26.1 points, 11.2 assists, 8.9 rebounds and 1.3 steals since moving to Brooklyn in January.

Harden's 11.1 assists on the year, including an initial stretch with the Rockets, lead the league, while an assist rate of 46.2 per cent trails only Russell Westbrook.

The superstar guard has taken an unselfish approach as the Nets aim for a championship, attempting 17.6 field goals per game in 2020-21 - his lowest rate since 2013-14 - and seeing his usage drop to 29.3 per cent, its lowest since the statistic was first tracked.

But Harden has still carried Brooklyn for long stretches while Irving and Durant have sat out, meaning head coach Nash was relieved to relay a major issue was not anticipated.

"We're going to monitor it. We'll see how he feels in the morning," Nash said. "I don't have a lot to tell you.

"We feel optimistic it's not a long-term thing and we'll just monitor it. I haven't spoken to him yet. I came in, addressed the team and then came to speak to you guys.

"I think he told the trainer when he was on the sideline and they went back to look at it and decided that it wasn't worth risking it. We'll just see how he feels in the morning and go from there.

"They just decided it wasn't worth risking him going back out there, but we haven't done any scans. We'll see how he feels in the morning and decide what the next step is."

Harden's problem could mean another reshuffle for a Nets team who, through injuries and trade, have had nine different starting fives this season.

That makes their achievement in reaching the top of the conference even more impressive, according to Nash.

"We're first and foremost really proud of our guys," he said. "They've had a lot thrown at them this year, we've had a lot of different lineups, a tough schedule and a new group - three new groups, in a sense.

"For them to stick together, to continue to pursue what we're asking them to pursue, big picture and in the short term with the details, it's impressive."

But Irving saw cause for concern in the Rockets win as Houston ran out to a 42-29 first-quarter lead before the point guard helped reel them back in.

Slow starts are a theme for Brooklyn, who led only one game through three minutes in the whole of March.

"We're going to get every team's best shot, so that's something that we've come to accept," Irving said.

"We know the game plan that we need to execute and it's up to us to go out and do it at a very high level.

"Sometimes we don't make that choice in the first four minutes or the first five minutes where we get down 18-6 or 18-4 and we're just digging ourselves out of holes on the scoreboard.

"I'm listening to the chatter from other teams on the court and they just continue to say, attack us, attack us, attack us, and I'm here on the court as well with all my team-mates just saying, it'll turn over for us.

"We've just got to be resilient, persevere through this, and we'll start making shots, but more or less it just comes with our effort.

"We've got to bring it from the first five minutes. In the last few games, we've failed to do so, so we played catch-up and we got away with this one, but against the great teams we know we've got to bring it from minute one."