Unable to contain Washington in transition, the Celtics surrendered 71 points in the first half and trailed by seven at the break.
But they out-scored the Wizards 36-16 in the third quarter to seize control, pushing their lead to as many as 15 points and holding off a late Washington rally to triumph 133-129.
Porzingis told NBC Sports Boston he didn't think the Celtics' first half was "all that bad."
"But the second half we knew we had to take away their transition," he said. "Second half we turned up our intensity."
Tatum said it might not have been pretty, but he was satisfied with the Celtics' 40th win of the season.
"We did a lot of good things out there and we had to figure it out," Tatum said. "But a win is a win, so we'll take it."
The Lakers scored 51 points in the second quarter and all five Lakers starters finished with at least 20 points.
In Sacramento, center Domantas Sabonis out-dueled Denver's two-time Most Valuable Player Nikola Jokic, posting his 16th triple-double of the season to propel the Kings to a 135-106 victory over the reigning champion Nuggets.
"As a competitor you always want to go against the best," Sabonis told NBC Sports California of taking on Jokic - who is now second behind Sabonis on the season triple-double list with 15. "Every matchup you get against him you've got that extra fire."
Sabonis connected on seven of his nine shots from the field on the way to 17 points, adding 17 rebounds and 10 assists.
Jokic led the Nuggets with 23 points but Denver missed a chance to edge ahead of Minnesota for sole the Western Conference lead.
Immanuel Quickley scored 25 points and RJ Barrett added 21 - Barrett's two free throws sealing the victory after Houston's Dillon Brooks cut the deficit to 105-104 with a three-pointer with 23.3 seconds remaining.
76ers 'hopeful' on Embiid
But Philadelphia, without reigning NBA Most Valuable Player Joel Embiid, who will miss at least a month after surgery to repair a meniscus injury in his left knee.
Sixers president Daryl Morey said before the game that the team remain hopeful that Embiid can return for a possible playoff run.
"We're hopeful," Morey said. "Feedback has been more good than bad since we first heard about what led to his procedure. So, we're hopeful and we're building the team to make it better this year."