England will be without both captain Owen Farrell and wrecking-ball No 8 Vunipola for their World Cup opener, against the physical and threatening Pumas, in Marseille on Saturday, September 9.
The absence of two vital cogs in head coach Steve Borthwick’s team creates an immediate selection headache for the critical encounter against Michael Cheika’s team.
Vunipola pleaded guilty to the charge of a dangerous tackle, having been sent off in Saturday’s 29-10 defeat by Ireland in Dublin.
The 30-year-old’s previous clean disciplinary record and his early acceptance of the charge led to a reduction from the six-week entry point penalty.
That cut any ban down to three weeks, and should Vunipola complete World Rugby’s tackle school coaching programme he will shave another match off his suspension.
Vunipola will miss Saturday’s final World Cup warm-up clash, against Fiji at Twickenham.
And provided he completes the tackle school course that means the only World Cup match he will miss will be the Argentina encounter.
“The player admitted that he had committed an act of foul play worthy of a red card,” read a Six Nations statement.
“On that basis, the committee applied World Rugby’s mandatory minimum mid-range entry point for foul play resulting in contact with the head.
“This resulted in a starting point of a six-week suspension.
“Having acknowledged mitigating factors including his exemplary previous record, immediate apology and remorse, and noted the absence of any aggravating factors, the committee reduced the six-week entry point by three weeks, resulting in a sanction of three weeks.
“The player may apply to take part in the coaching intervention programme to substitute the final match of his sanction for a coaching intervention aimed at modifying specific techniques and technical issues that contributed to the foul play.”