Chelsea succeeded in transplanting their potent Cup form into a strangely becalmed Premiership campaign, leaving Palace firmly rooted at the foot of the table as they did so. It was almost as if they were provoked by a glimpse of the impertinence of Palace's early season away form, because after Hermann Hreidarsson had given the visitors the lead they struck back in devastating style.
The Icelander drove home from the angle of the penalty area after Chelsea had failed to clear their lines; but it was nothing to the defensive fallibility which was to follow.
Chelsea punished what is still, for the moment, Steve Coppell's side twice in as many minutes in their first flurry, Vialli pouncing for his first when nobody volunteered to clear Gianfranco Zola's corner and Zola himself claiming the second as he rounded Kevin Miller with consummate ease.
David Tuttle thought he had headed an equaliser when he met Simon Rodger's free-kick only to be ruled offside, but Palace were cast hopelessly adrift just before the break when Miller failed to hold the ball with Vialli buzzing around him, leaving the player-manager to push in his second.
Palace brought on three forwards in the second half, including Attilio Lombardo, who was hailed as a potential saviour by their little phalanx of fans, but their need to throw everyone forward made their vulnerable defence even more flimsy.
Chelsea had been guilty of over-elaborating when presented with some opportunities and Dennis Wise had seen an overhead kick brilliantly saved by Miller before a late burst showed that their subsidiary business of maintaining a decent League position was back on the tracks.
First Wise stroked the ball home and then after another of Palace's reinforcements, Marcus Bent, had replied, Tore Andre Flo helped himself to a rapid double. That made it four goals in a frantic last six minutes, but Chelsea had actually defined the difference between the two sides long before that.
Coppell, who saw his best defender, Andy Roberts, sold from under him at the weekend, pointed to a clear moral. "I thought there were spells when we were brighter than we've been for a long time," he said. "But we were so fragile in defence it was unbelievable. You can't blame off- field activities for rank bad defending, for people playing offside in the wrong part of the pitch. We were 11 strangers tonight defensively."
Chelsea (3-5-2): Kharin; Sinclair (Lambourde, 80), Leboeuf, Clarke; Petrescu, Morris (P Hughes, 84), Wise, Newton, Granville; Zola, Vialli (Flo, 74). Substitutes not used: Charvet, Hitchcock (gk).
Crystal Palace (3-5-2): Miller; Ismael, Edworthy, Tuttle (Bent, 78); Smith, Emblen (Lombardo, 65), Fullarton, Rodger, Hreidarsson; Dyer (Jansen, 65) Brolin. Substitutes not used: Linighan, Nash (gk).
Referee: M Riley (Leeds).