New Zealand's sorry Australian tour took another turn for the worse as Trent Boult was ruled out of the third and final Test in Sydney with a fracture on his right hand, sustained while batting.

Boult had been struck on the gloves by Mitchell Starc at the back-end of New Zealand's first innings at the MCG, and went to hospital for x-rays during the tea break. The results confirmed a fracture, meaning Boult will fly home after the Melbourne Test and be out for at least four weeks, although he did return to bowl towards the end of the day.

"Trent Boult suffered a fracture to the second-metacarpal of his right hand after being struck while batting on day three of the second Test against Australia in Melbourne," a New Zealand Cricket spokesperson said. "An X-ray during the tea break confirmed the undisplaced fracture which will require around four weeks of rehabilitation, meaning Boult will return home to New Zealand at the end of the Test. A replacement player will be confirmed in due course."

Boult had missed the first Test of the series, in Perth, because of a side injury, but recovered in time to play the Boxing Day Test.

Opening batsman Tom Latham said that Boult's recent run had been "gutting" for the left-armer and the team as a whole.

"It's obviously gutting news for Trent and also for our group to have someone like that ruled out with his injuries," Latham said. "We'll have to wait and see who the replacement is over the next few days, but I'm sure whoever will come in will be up for the task."

Boult is the second New Zealand bowler to fly home from the tour following the injury sustained by Lockie Ferguson in Perth. Their next cricket after the Sydney Test is the T20I series against India which begins in late January and is followed by ODIs and two Tests in February.