Josh Giddey has scored an NBA career-high 31 points but will be wishing he added one more after Oklahoma City's potentially costly 137-134 home loss to Charlotte.
The 20-year-old Australian was one of three Thunder players to achieve personal bests, Isaiah Joe with 33 points and Jalen Williams 31 in the absence of All-Star Shai Gilgeous-Alexander (ankle).
But Williams, then Giddey each missed one of two free throws in the final 16 seconds.
Giddey would have tied the game by making his second attempt.
But the rebound was collected by the Hornets, who then added two more points before Williams' rushed three-pointer attempt to send the game to overtime missed the mark.
Giddey passed his previous best of 28 points when he dunked late in the fourth quarter.
He also had 10 rebounds and nine assists, shooting 14-of-22 from the floor.
The Thunder had led by 11 but found themselves down by 13 before rallying to tie the game late in the final quarter.
PJ Washington scored 22 of his career-high 43 points in the fourth quarter for the visitors.
The Thunder were looking to strengthen their position in the ultra-tight Western Conference play-in tournament race.
Instead, they sit in 10th and occupy the last play-in spot ahead of Dallas, who boast an identical 37-39 record after twice falling to the lowly-ranked Hornets (26-51) recently.
"We got up 10 and I think we got complacent," Giddey said.
"We've got to understand the teams we're playing against ... they're not in the race, they've got nothing to lose out here.
"We have to buckle down and understand what we're playing for and what the stakes are."
As it stands the Thunder would meet LeBron James' Lakers in the first play-in round from April 11, needing to beat them and then the loser of Golden State-New Orleans to earn a surprise play-offs berth.
