Australian guard Dyson Daniels has continued his breakout season with a career-high 28 points in Atlanta’s huge upset of reigning champions Boston in their NBA Cup opener.

The Hawks, without injured star Trae Young, trailed by eight points early in the final quarter but rallied to post a 117-116 win over the Celtics at TD Garden.

Daniels missed a floater in the dying seconds, but it was tipped in by teammate Onyeka Okongwu, who gave the Hawks their first lead since the first quarter.

The teams traded turnovers on in-bounds passes before Boston’s game-high scorer Jaylen Brown (37 points) pulled up from 13 feet and shot off the rim with his attempted game-winner.

Daniels, the league’s leader in steals, top-scored for Atlanta and added seven assists, six steals and three rebounds in an outstanding display.

“We knew it was going to be tough, coming in against the defending champs, but we fought,” Daniels said after the game.

“We fought until the end. They got us in the first half and we went down 15 or something, but we kept our heads up, kept fighting, and credit to the team.

“Coming in here people were probably counting us out, but we didn’t count us out.

“We came in here, we did our job, we did what we needed to do.”

The 21-year-old Bendigo product’s previous career-high points tally was 18, recorded against Charlotte earlier this season.

Jalen Johnson (18 points, 13 rebounds, 10 assists) also shone for Atlanta, with Larry Nance Jnr (19 points) and Clint Capela (18) also effective.

Brown got strong support from Derrick White (31) and Jayson Tatum (20) for Boston, who opened the in-season tournament on a green floor with a parquet design.

In Detroit, Malik Beasley made a tie-breaking free throw with 1.1 seconds left in overtime as the Pistons edged Miami 123-121.

The Heat were handed a technical foul for calling a timeout when they had none left, allowing Beasley to give Detroit the lead.

He added another free throw with 0.1 seconds left to complete the win.

Beasley and Cade Cunningham scored 21 points each for the Pistons, while Tyler Herro had 40 points for Miami, including 20 in the last quarter.

Franz Wagner top-scored for Orlando Magic in their 114-89 win over Charlotte.

The Hornets were well-served by former NBL Next Star LaMelo Ball, who scored a game-high 35 points.