On a day when England and Wales finished a familiar close second to New Zealand and Australia respectively, Ireland under Joe Schmidt struck a mighty blow for the home countries. In the great global scheme of things, it very nearly changed the pecking order of the established hierarchy.
Ireland would have been rewarded with a place in the top three of the IRB world rankings had JP Pietersen's last-minute try not forced the mathematicians to shave a fraction off Ireland's winning percentage.
O'Connell, who has started only three games in the GUINNESS PRO12 this season, has been the one constant in all four Irish victories over the double World Cup winners, from last Saturday's emphatic success all the way back to Lansdowne Road in 2004 when South Africa lost 17-12 and Ronan O'Gara accounted for every Irish point.
It puts 'The Big Red Monster,' as O'Gara nicknamed his Munster colleague, in the same exalted league as one of his predecessors as captain of the Lions, Martin Johnson. Leicester's supreme second row forward managed six Test wins over the Boks during the five years which ended with England's World Cup triumph in Sydney in 2003.
While Johnson achieved two of those six south of the Equator, in Perth en route to the final and in Bloemfontein three years earlier, O'Connell's winning quartet have all taken place in Dublin, albeit at three venues - the Aviva Stadium, Lansdowne Road and at Croke Park on a misty day in 2009.
His opposite number so often over the last decade, Victor Matfield, knew that last Saturday meant mixing it not just with a formidable old foe but the most formidable one the ever-lasting Springbok had come up against.
'I think he's probably the best player I've played against in my career,' Matfield said before the match. 'You can see that he puts in a lot of hours analysing, preparing and getting his whole unit ready. So it's always tough going up against him.'
Last Saturday would have been tougher than most in a rivalry which stretches back all the way to their first encounter, on the High Veldt at Bloemfontein when a 31-17 home win gave the Boks' new coach, Jake White, a winning start to a run which would take him all the way to a winning Rugby World Cup final against England in Paris three years later in 2007.
There can never have been a meeting of two such second row titans to compare with the one last weekend - two players with a combined total of 220 Test appearances (Matfield 118, O'Connell 102) and a combined age of 72 (Matfield 37, O'Connell 35).
Perhaps there will be one final rematch on what would be the biggest stage of all, in the final stages of the Rugby World Cup at Twickenham next year. If they win their respective pools, Ireland and South Africa can only collide in the final by which time the venerable Matfield will be all the more so, having turned 38.
O'Connell hasn't got where he is today by wasting any time on flights of fancy. His reaction to last Saturday's triumph against the odds, at least those offered by the bookmakers, was typical of the man.
'It's a massive win but I suppose that's all it is, a Test win,' he said. 'To get it against one of the Southern Hemisphere teams is massive for us. There's a lot of things to improve on and that's what we'll try to do.'
Australia in Dublin on Saturday week presents Ireland with the novel challenge of coping with a public expectation raised by the high level of smart thinking which went into last week's win. Every aspect was impressive, none more so than the collective discipline which ensured they did not concede a single penalty during the last quarter, a period when the Boks conceded six.
Once he has attended to this week's business in France after a winning start as the Wallabies' head honcho, Michael Cheika will be back on familiar ground in Dublin. The former Leinster coach will not need anyone to tell him what to expect.
Despite his team having been out-scored 4-3 on tries over the course of a rip-roaring Test match, Cheika still had the satisfaction of presiding over Australia's tenth straight win against Wales.
The Wallabies still made it despite trailing in the first five minutes and again going into the last ten. In between, Wales came from behind three times and had their opponents draped over the ropes after scrummaging them into the submission of a penalty try.
Bernard Foley's astute control ensured that the Wallabies won it in the final moments yet again. His had been a complete fly-half performance surely without equal until Jonny Sexton raised the art to an even higher level a couple of hours later.
England's record against New Zealand is identical to Wales' against Australia - one win out of eleven. Jonny May's electrifying solo try raised the early prospect of something different which it might have been had Mike Brown taken Kyle Eastmond's pass before half-time.
The subsequent cloudburst above Twickenham turned out to be merely the cue for the All Blacks to show what they have shown on countless occasions over the years, that nobody plays wet-weather rugby the way they do. In doing so, they ensured that Dane Coles' yellow card cost them nothing.
Richie McCaw's 25th Test try helped secure his 119th win from 135 internationals. His captaincy record is, if anything, marginally more phenomenal - Played 98, Won 86, Drawn 2, Lost 10.
This week finds him back in his ancestral home preparing for Scotland at Murrayfield, where, of course, he has never lost. The Scots under Vern Cotter rewarded their new coach with a 41-31 win over Argentina, five tries including one each for the Gray brothers, Richie and Jonny.
Theirs was the first fraternal Scottish double since the Hastings boys, Gavin and Scott, touched down against Tonga at Pretoria during the 1995 World Cup.
Italy's 24-13 win over Samoa was also hailed loudly after their unwelcome losing streak came to an end. They face the Pumas next time out and that will be an even closer Test.
Best XV of last weekend?
15 Israel Folau (Australia)
14 Tommy Bowe (Ireland)
13 Tevita Kuridrani (Australia)
12 Sonny Bill Williams (New Zealand)
11 Jonny May (England)
10 Jonny Sexton (Ireland)
9 Conor Murray (Ireland)
1 Jack McGrath (Ireland)
2 Richard Hibbard (Wales)
3 Samson Lee (Wales)
4 Sam Whitelock (New Zealand)
5 Paul O'Connell (Ireland)
6 Peter O'Mahony (Ireland)
7 Richie McCaw (New Zealand)
8 Kieran Read (New Zealand)
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