How it happened: The Mavericks managed to blow a 23-point second-half lead, an unbelievable collapsed even by the standards of Dallas’ disturbing recent playoff history.

The Mavs built that lead with dominant defense, which completely disappeared during the fourth quarter.

Portland, which opened the game by matching the lowest-scoring quarter in franchise playoff history, poured in 35 points during the final frame to stun the Mavericks and even the series.

Brandon Roy simply took over the fourth quarter, single-handedly outscoring the Mavs in the last dozen minutes. Roy had 18 of his game-high 24 points in the fourth, hitting eight of 10 shots from the floor, including a game-winning bank shot off the dribble.

What it means: The Mavs will have to get over a demoralizing loss during the four-hour flight back to Dallas. They’re also guaranteed to have to make a return trip to the Rose Garden for Game 6.

Play of the game: Shawn Marion had just made a nice post move to momentarily stop the bleeding when he committed a bonehead foul, bumping Brandon Roy on a 3-point attempt. Roy hit the shot and the free throw for a four-point play with 1:06 remaining, completing Portland’s comeback from a 23-point deficit.

Stat of the day: The Blazers missed 17 consecutive shots during a span of 12:06, including the first 10-plus minutes of the second half. They responded by making their next eight attempts to begin the epic comeback.