It raises questions about whether the potential No.1 overall NBA draft pick's time on an NBL court is done, although the Australian league says that isn't the case.

Hawks coach Matt Flinn was tight-lipped on the extent of Ball's injury after he missed Saturday's 10-point loss to Brisbane due to a sore foot.

However the NBL confirmed on Monday the NBA draft prospect bruised his foot during a recent practice and won't be back until the new year.

The confirmation came hours after Illawarra announced the signing of American forward Billy Preston as a replacement for the injured Sam Froling.

Preston is the second import to sign with the Hawks in the past week, with former NBA swingman Darington Hobson set to make his debut next Monday.

Hobson was signed as a replacement for the injured Aaron Brooks.

The developments are likely to fuel speculation Ball may pull the plug on his stint in Australia and begin preparations for the 2020 NBA draft.

Numerous draft pundits predict the 20-year-old could be the No.1 overall pick.

The NBL Next Star has averaged 17 points, 7.5 rebounds and 6.8 assists in 31 minutes per game so far for the Hawks.

However the NBL is confident Ball will finish the season with Illawarra.

"Ball will rehab his injury in Australia and is expected to make a full recovery and continue to play for the Hawks for the remainder of the season," the NBL said.

Preston arrives in Wollongong after playing in the G-League, where he averaged 7.1 points and 4.4 rebounds in 17.6 minutes a game across three teams.

The 22-year-old made headlines last year when he was embroiled in a NCAA scandal that involved his family allegedly being given money by Kansas University.

The saga forced him to quit the college program and play professionally in Bosnia before going undrafted in 2018.

Australian Associated Press