Richardson scored five of his 38 points in that tiny span and, thanks to a made free throw that Rudy Gay intended to miss, the Suns forced overtime and stole what seemed a certain Memphis victory.
"I haven't done that in my lifetime," Richardson said. "That was just a crazy turnaround. They thought they had a win. I guess the basketball gods were on our side."
Steve Nash scored 13 of his 25 points in the overtimes to send Memphis to its third loss in a row.
Memphis seemed safely ahead when O.J. Mayo's two free throws made it 98-94 with 3.7 seconds left in the fourth quarter.
But Richardson banked in a 3-pointer to make it 98-97 with 1.1 to go, then Nash fouled Gay on an inbound pass. The referees put 0.4 seconds on the clock.
Gay missed the first free throw and clearly intended to miss the other so time would run out. But it went in and, after a timeout, the ball moved to Phoenix's frontcourt and Grant Hill lofted a perfect lob to Richardson at the rim. The shot went in to tie it at 99.
"Grant threw a great pass," Richardson said. "He's known for great passes. He threw one to Christian Laettner to win the game (for Duke against Kentucky 18 years ago) so he threw a great pass up there and I almost missed the layup, the dunk or whatever you want to call it, but I'm glad it rolled in."
Memphis was without head coach Lionel Hollins and assistant Johnny Davis, who attended the memorial service for former teammate Maurice Lucas. That left assistant coach David Joerger in charge.
"I might have played guys too many minutes," Joerger said. "I don't know. Maybe that's why we missed some free throws."
Gay blamed the loss on "a couple of immature mistakes," especially the made free throw.
"I was trying rim it off the front so I could give my team a chance to tip it out," he said.
Instead, it was perfect.
"It was a lot of weird things that happened in that game," Mayo said, "some controllable, some uncontrollable. It was a tough loss to take."
Richardson's sixth 3-pointer in seven attempts put Phoenix ahead for good in the second overtime. Nash followed with a pair of short bank shots and the Suns led 116-110. A rare missed free throw by Nash gave Memphis a shot at tying the game, but Gay misfired on a 3-pointer with seven seconds left and Phoenix put it away with free throws.