PORTLAND, Ore. — Brandon Roy’s season had been fraught with uncertainty, first over the stability of his knees, then over his diminished role with the team.

All those doubts melted away on Saturday when he led the Portland Trail Blazers to one of the greatest comebacks in NBA playoff history.

With 39.2 seconds left, Roy made a go-ahead bank shot that gave the Trail Blazers a stunning 84-82 comeback victory over the Dallas Mavericks — and evened their first-round playoff series at two games apiece.

Roy finished with 24 points — 18 in the fourth quarter alone — as the Blazers erased a 23-point deficit. Portland became the third NBA team in the shot clock era to win a playoff game when trailing by 18 points or more heading into the fourth quarter.

“I’ve been in some pretty good zones before,” the three-time All-Star said. “But nothing like tonight.”

After the victory, Roy was swallowed by the embrace of several of his teammates.

“It still just doesn’t feel real yet,” he said. “It was just an unbelievable game and comeback. With everything I’ve been through this season, they just all came into that moment there on the court when guys we’re grabbing and cheering me on. It was real special.”

Trailing 67-44 in the third quarter, the Blazers closed the gap to 77-70 after Roy’s step-back jumper.

Jason Terry answered with a 3-pointer but then Roy drove down the lane and finished to narrow it to 80-74 with 2:32 to go. LaMarcus Aldridge added a turnaround jumper.

Roy traded baskets with Shawn Marion before making a 3-pointer and a free throw with 1:06 left to tie it at 82.

After Roy’s go-ahead jumper from out front banked in, the Mavericks missed two 3-point tries, the first from Jason Kidd and the second from Terry as time ran out. Roy defended Terry on the final shot.

Dirk Nowitzki had 20 points to lead the Mavericks. Terry finished with 13 off the bench.

Aldridge finished with 18 points for the Blazers, while Gerald Wallace had 10 points and 11 rebounds.

“When people ask me what did I do in the fourth quarter, I’ll tell them ‘I stood in the corner and watched The Brandon Roy Show,'” Wallace said.

The series now heads back to Dallas for Game 5 on Monday.