Biggest upset in NBA history?

If the Lakers do the unthinkable, if they fail to defeat the Oklahoma City Thunder in their first-round playoff series, will it be the biggest postseason upset in NBA history? Eighth-seeded teams have beaten top-seeded teams in the past, but the Lakers also are the defending champions, a team that’s made consecutive trips to the Finals. The Thunder are a team with almost zero playoff experience. The series is deadlocked at 2-all.