He made sure one at the end of regulation didn't have a chance as he stepped up big against Jameer Nelson.
Harris' block kept Utah alive, and in the end it was the Jazz draining 3s to secure a 117-107 overtime victory over Orlando.
"We survived, that's the best way to describe it," said Utah swingman Gordon Hayward, who along with Harris hit key 3-pointers in overtime. "All season long we've been fighting. We needed this one badly."
The victory allowed the Jazz (34-30) to keep their lock on the final Western Conference playoff spot.
The Jazz can secure a postseason berth with a win Tuesday night at home against the Phoenix Suns (33-31), who hold the tiebreaker against the Jazz but are a full game behind after their loss to Denver earlier Saturday.
"Steve Nash is going to do the same thing (as Nelson) and get his guys the ball," Jazz center Al Jefferson said referring to Nelson, who had 11 assists to go along with his team-high 23 points Saturday. "But we just have to grind it out and play hard and get some hands up in his face."
The Magic (36-27) must regroup after dropping their second straight and first since All-Star center Dwight Howard had back surgery that will keep him out until next season.
The Magic also have been without forward Hedo Turkoglu, who had surgery April 9 for a fractured cheekbone, and is questionable for the playoffs.
Combined, the two accounted for 31.3 points and 18.3 rebounds. Saturday the Magic also were without 6-foot-10 forward Earl Clark because of a sore left knee
Despite the missing pieces, Orlando coach Stan Van Gundy ripped into his team.
"We just cannot guard, we cannot," Van Gundy said. "I don't think that our guys are not trying, but we cannot guard anyone. Our defense is disturbing to say the least."
Van Gundy also had harsh words for backup center Daniel Orton, who contributed only two points off the bench.
"Daniel gave us nothing," Van Gundy said. "He went for every shot fake, he fouled every time. He didn't even give us minutes that we needed to give our starters some rest. Our lack of depth was an absolute huge factor. Those guys ran out of gas at the end."
The Magic made just 2 of 8 shots in overtime and were 0 for 3 from beyond the arc.
Overall, the Magic made 15 3-pointers on the night and the Jazz just four, but Utah's two in overtime made the difference.
"I didn't believe a team could shoot like that the whole game," Jefferson said.
Richardson started 6 of 6 for the Magic, including 3 of 3 from beyond the arc, as the Magic jumped out to a 36-23 lead on 65 percent shooting.
The Jazz trailed by 14 in the first half, by 12 in the third and by six midway through the fourth. But each time they rallied.
Jefferson's jumper tied it at 101 before Harris' big block, and Jefferson also scored the first points of overtime on a nice move around center Glen Davis -- finishing with 21 points, 10 rebounds and three blocks
It was Davis who suggested the motto "We all we got" as the injury-riddled Magic head into the final stretch before the playoffs having already secured a spot.
Early in Saturday's game, that was working as they jumped out to a huge lead.
The Magic led by as many as 14 in the second before a 10-0 Jazz run.
Derrick Favors started the run with a short jumper and ended it with a powerful dunk that got Utah within 43-39.
Favors gave Utah a 53-52 lead on crowd-pleasing reverse dunk in traffic.
Utah took advantage of its four big men to hurt Orlando.
"A three guard can't guard Paul on the post and he did what he had to do. Al Jefferson was finishing around the rim and I came in with defensive energy," said Favors, who finished with 16 points and 11 bounds off the bench.
Millsap added 18 points and Kanter nine.
The score was tied at 55 at the break, and the Jazz opened on a 12-7 run to take a 67-62 lead in the third only to see Orlando respond with a 16-0 run to surge ahead 78-67.
Nelson hit a pair of 3-pointers, while J.J. Redick and Anderson each hit a 3 during a four-minute span where the Jazz went scoreless.
Utah closed on a 14-5 run, sparked by DeMarre Carroll's 19-footer, Favors' put-back and Hayward's three-point play.
Favors would come up with another key block in the fourth, and jam off a pass from Harris before Jefferson's tying 12-footer with 21 seconds remaining.
"Nothing is easy," Jazz coach Tyrone Corbin said. "This bunch of guys. ... I can't say enough about how they gutted it out again and laid everything on the line. Even when we got down, nobody was discouraged."
Turkoglu traveled with the Magic, his first road trip since he underwent surgery April 9 to repair a fractured cheekbone. .... Jazz Hall of Fame coach Jerry Sloan attended his first Jazz game since he abruptly resigned Feb. 10, 2011. He sat near midcourt, about four rows up. ... Jamaal Tinsley's assist to Kanter at the 8:46 mark of the second quarter was the 3,000th of his career. ... Utah outscored Orlando 62-36 in the paint. ... The Magic had five players score in double figures for the 30th time this season.
Cleveland busts open Game 5 early as they end the first quarter on a 17-3 run against the Raptors to stretch their lead to 18 points.
Jalen Rose and David Jacoby break down Draymond Green's performance against the Thunder and offer some advice.
LeBron James finds Richard Jefferson rolling to the basket for the high-flying two-handed slam dunk.