Aron Baynes will require surgery after breaking his left hand in the Boston Celtics' clash against the Phoenix Suns today.

It is believed the Aussie centre suffered the injury after fighting for a rebound with Suns centre Deandre Ayton in the first quarter.

Baynes was taken down the tunnel during the game, and the Celtics have since diagnosed the injury as a fourth metacarpal fracture.

While the team announced Baynes would be out indefinitely, The Athletic's Shams Charania, who first revealed the news, said the 32-year-old is expected to return in a month.

It is a frustrating development for Baynes, who has already missed time this season with an ankle injury.

The Aussie is averaging 5.5 points and 4.4 rebounds in 14.8 minutes off the bench. He has been an important piece of the Celtics' front court, especially with the absence of Al Horford.