Blues captain Keven Mealamu was hit "flush in the back of the head" by a bottle filled with water as a disgruntled Bulls spectator delivered his displeasure at the Loftus Versfeld arena.
Team physiotherapist Mark Plummer, Bulls wing Bjorn Basson and a touch judge shielded Mealamu as the confrontation threatened to escalate after the final whistle.
Team manager Bryce Anderson said last night from South Africa that while the bottling hurt, Mealamu wasn't injured, just shocked.
The invasion came after Blues wing Rene Ranger clobbered Basson with a dubious tackle as the wing dived in at the corner for a try.
As Basson recovered and went to join his teammates he remonstrated with the spectator who had confronted Mealamu.