The second-round of the NBA Playoffs will open with a matchup everyone has circled on the calendar for weeks. The Bucks, fresh off a resounding sweep of the Heat in the first round, will take on the Nets, led by the big three of Kevin Durant, James Harden, and Kyrie Irving—who some believe to be the most dominant offensive trio ever assembled.

The Nets have the better top-end talent, but their big three have only played together for very brief stretches this season. Meanwhile, the Bucks delivered a very clear response to the haters in the first-round and have a much-improved supporting cast surrounding Giannis Antetokounmpo, led by point guard Jrue Holiday.

It is not even a hot take to say this second-round matchup might determine this year’s NBA champion. We’ve seen this kind of epic matchup early in the playoffs before (ask Nets head coach Steve Nash about his 2007 second-round matchup against the Spurs). A serious championship contender will be bounced of the postseason earlier than many expected.

That means either the Nets or Bucks will join a dubious list of teams that will be left wondering “what if?”

The list of championship-caliber teams to not win a title over the past 20 seasons is littered with squads that were full of talent, but ultimately unfulfilled promise. That’s baketball sometimes as Bucks fans—who can point to their team two seasons ago that reached the Eastern Conference Finals and took a 2-0 lead on the Raptors—know all too well.

Here are the most memorable “what if” NBA squads since 2000.