Rakell received a long pass from defenseman Brandon Montour at the Edmonton blue line and skated in on Koskinen, who made the initial save with his right pad. Rakell pushed the rebound in for his 100th NHL goal.
It was the fourth time in the past 18 months the Ducks have tied the score against the Oilers after pulling their goalie for the extra skater.
Anaheim came back from trailing 3-0 in Game 5 of the 2017 Western Conference Second Round by scoring three goals in the final 3:16 of the third period. The Ducks won 4-3 in double overtime to take a 3-2 series lead and won it in seven games.
On Feb. 25 in Anaheim, Rakell tied it with two goals in the final 21 seconds of the third, but Edmonton won 6-5 in the shootout. On March 25 in Edmonton, Adam Henrique scored with 1:29 left in the third to tie it 4-4, and the Ducks won 5-4 in overtime.
Ritchie tied the score on a rebound Friday after Marcus Pettersson's shot from the point went into a crowd in front of the net and the rebound landed at Ritchie's feet.
"We stuck with it at the end there," Henrique said. "Ritchie did a great job just getting out front and finding a way to put that one in."
Nugent-Hopkins scored on the power play to give the Oilers a 1-0 lead at 8:55 of the third.
Alex Chiasson brought the puck down the right side and passed to Connor McDavid in the middle, where McDavid passed to Nugent-Hopkins on his left. Nugent-Hopkins' shot from the left face-off circle glanced off the inside of the left post and into the net.
The Ducks thought they took a 1-0 lead at 5:29 of the third. Henrique took a shot from the left circle that got through Koskinen, hit the right post and was tumbling on the goal line. Anaheim forward Pontus Aberg was in position to push the puck across, but Edmonton defenseman Kris Russell pulled it back into Koskinen.
