CLEVELAND — Cavaliers starting guard J.R. Smith will be out indefinitely with a broken right thumb, an injury that will test the depth of the defending NBA champions.

Smith got hurt late in the second quarter of Tuesday night’s game in Milwaukee and didn’t return after halftime in a game the Cavs won 114-108 in overtime. X-rays taken after the game were inconclusive, but further tests done Wednesday in Cleveland revealed the fracture.

The Cavs aren’t putting a timeline on know how long Smith will be sidelined. Typically, injuries like Smith’s require at least one month of recovery time, but the severity of the break is not known and his return date won’t be determined until after the operation.

The team did not say when Smith will have surgery.

Smith’s injury is the latest and most serious medical setback for the Cavs, who are 20-6 going into Wednesday’s home game against the Bucks. Power forward Kevin Love, who is having an All-Star season, missed Tuesday’s game with a bruised knee and reserve center Chris “Birdman” Andersen suffered a season-ending knee injury last week in practice.

With Smith out, coach Tyronn Lue will have to balance not overworking stars LeBron James and Kyrie Irving and finding offense elsewhere.

Cleveland has some current roster issues with Andersen and Mo Williams (knee surgery) taking up two spots. The Cavs have been in the market to find a backup point guard — Iman Shumpert and James have been getting some of those minutes — and could now be forced to find another wing player.

advertisement | advertise on newsday

The good news for the Cavs is that the injury happened now and not deeper in the season.

Smith has become a fan favorite in Cleveland. He had a major role in the Cavs beating Golden State in last season’s NBA Finals, dropping two big 3-pointers in Game 7, and then became something of a cult figure when he showed up shirtless to the team’s celebratory downtown parade.

He held out of training camp for a new contract, and the Cavs eventually signed him to a four-year, $57 million deal.

Smith has had a bumpy start this season, missing five games with an ankle problem and hyperextended knee. He is averaging 8.6 points but has been slowly emerging from a shooting slump.