Celtics’ failure needs study in the third degree

■ A 19-0 Orlando run over a 5:12 period;

■ The Celtics were without a field goal over the final 7:16, a total of 8:15 spanning the final two quarters;

■ The Magic’s dominance extended to 28-2 over a 7:28 period spanning the third and fourth, Mickael Pietrus’s 3-pointer 29 seconds into the fourth making it 79-62.

“We were getting what we deserved,’’ Celtics coach Doc Rivers said of the third quarter. “I thought we played [very badly]. In the third quarter, I thought everything we did in the first half we decided not to do. I thought we lacked discipline. I think right now, when you look at our team, I say I love our team on paper. But we tend to be front-runners - when we get a good lead, we relax and teams take advantage of it.’’

In fact, the Celtics outscored the Magic in three quarters. The Celtics took a 51-40 halftime lead and actually started the second half strong.

Kevin Garnett (13 points) hit three shots, including an alley-oop dunk from Rajon Rondo, as they maintained their halftime margin. But, after Garnett’s 20-footer gave the Celtics a 57-46 lead 2:56 into the half, the Celtics would get only one field goal - a Rondo 3-pointer at the shot-clock buzzer - for the remainder of the quarter.

Orlando had little difficulty defending the Celtics’ half-court offense, a Magic defender seeming to show up on a spot simultaneously with a Celtic. That left the Celtics in a freelance mode with little time on the shot clock. That is definitely not their style.

The Magic established their offense by isolating Dwight Howard against Kendrick Perkins, and once the low-post game was established, Orlando was able to pick its spots from the perimeter. Also, crucially, even after Howard (16 points, 13 rebounds) committed his fourth foul (with 5:58 left in the third), coach Stan Van Gundy allowed him to remain in the contest.