The Nets packed a bunch into their season opener, going from blowout loss to gritty win to heartbreak at the buzzer.

By the time Cam Thomas missed an off-balance 3-pointer and Cam Johnson a desperate put-back attempt at the buzzer, Brooklyn had suffered a tough 114-113 loss to Cleveland in front of a sellout crowd of 17,931 at Barclays Center.

The Nets had erased a 13-point first-quarter deficit and had a six-point cushion in the fourth.

They led with 14 seconds left until Westchester native Donovan Mitchell — whose name will be linked in trade rumors with both New York teams — drilled a 3-pointer to put Cleveland ahead.

Brooklyn missed not one but two looks.

Thomas poured in 36 points — tied for the most off the bench in a season opener in NBA history — including 24 in the first half.

But he missed a 3-point heave, and Johnson couldn’t pull off an acrobatic putback attempt.

Mikal Bridges had 11 of his 20 points in the fourth quarter, but it went to waste as they blew the lead.