The Oilers, however, had other plans, resurrecting themselves 21 months later, winning the Stanley Cup for a fifth time, the first time without "The Great One" in the lineup.
Edmonton was no doubt still a contender without Gretzky, but it was hard to imagine the Oilers picking up the pieces in the manner they did.
Looking back on it 25 years later, Oilers defenseman Charlie Huddy said it shouldn't have been that surprising.
"A lot of people thought we wouldn't be able to overcome losing him and what he did for us, but look at the guys we still had," Huddy told NHL.com. "We just had to get through the initial shock, get over it as players and move on. It took us a bit, but that's what we ended up doing."
Gretzky was gone and, obviously, was irreplaceable, but the Oilers had seven players (Mark Messier, Jari Kurri, Glenn Anderson, Kevin Lowe, Randy Gregg, Grant Fuhr and Huddy) from the previous four Stanley Cup championship teams. Esa Tikkanen, Craig MacTavish, Steve Smith and Craig Muni were part of back-to-back title teams in 1987 and 1988.
Craig Simpson, at 23, broke through to lead the NHL with 16 goals in the 1990 Stanley Cup Playoffs. His 31 points tied him with Messier for the League lead.
Bill Ranford, 23, took over for Fuhr in goal and was superb, posting a 2.53 goals-against average and .912 save percentage.
"I think the players felt pretty strongly that there was still a large nucleus of the team still in place, but nobody expected us to win another Stanley Cup," Ranford told NHL.com. "That just showed the amount of determination that the group had to prove everybody wrong."
The feeling of being an underdog served as a motivator, Huddy recalled.
"We lost a big part of our team, but we still had a lot of chemistry there and I think it was something that the guys wanted to prove that, yeah, we lose a great hockey player, but we're still a pretty good hockey team," Huddy said. "You always want to prove people wrong when they write you off."
Before the Oilers could prove they were still the class of the League without Gretzky, they had to go through the evolution of becoming a championship team again. That's what the 1988-89 season was for, and it wasn't easy.
After finishing with 99 points in the 1987-88 regular season and winning the Stanley Cup that spring, the Oilers dropped to 84 points the following season and were knocked out in the first round of the playoffs, in seven games by Gretzky and the Kings.
It was a devastating loss, and it showed they had fallen exactly the way many people across the NHL expected. The comparisons to the Gretzky-led teams of Oilers legend were impossible to ignore.
"We had to pick away at the season," Huddy said. "It didn't end the way we wanted, but it gave us a little bit more motivation for the following year. We had some more drive, a lot to prove."
When the 1989-90 season arrived, the Oilers no longer felt the weight of the what-ifs regarding Gretzky. Huddy said he doesn't remember nearly as many Gretzky questions from the media the second time around.
Gretzky was gone and he wasn't coming back. The time to move on was at hand.
The Oilers did, putting up 90 points in the regular season. In the playoffs, the adversity that could have easily broken them arrived. Edmonton fell behind 3-1 to the Winnipeg Jets in the Smythe Division Semifinals.
"It really forced us as a group and a team to play at a level that we hadn't previously played at," MacTavish told NHL.com. "We overcame that 3-1 deficit, and from that point forward we were as dominant a team as any of the previous Cup teams I had been on with Wayne."
In the next round, the Oilers swept Gretzky and the Kings before defeating the Chicago Blackhawks in six games to return to the Stanley Cup Final. In Game 1, Edmonton got a triple-overtime winning goal from Petr Klima at Boston Garden and went on to defeat the Boston Bruins in five games.
"He was the best player in the world," Ranford said of Gretzky. "To lose him, obviously you're going to be a little skeptical of being able to continue on, but the team found a way."
Follow Dan Rosen on Twitter: @drosennhl