Dan Jones is a fly half from Carmarthenshire whose Scarlets are two points behind in third place. Sammy Arnold is a wing whose Ulster team are up to fifth, Zander Fagerson a Scottish prop helping the Warriors defend their title, Jarrod Evans a fly half at Cardiff Blues and Sam Underhill a flanker at the Ospreys.
As 19-year-olds, the six are worthy of special mention. O'Donnell, a first-year member of the Connacht academy, appeared during the final quarter of the home win over Benetton Treviso as he had done against Zebre a fortnight earlier and in the last minute against the Blues at the start of last month.
A whole host of other youngsters are breaking through right across the competition. Nobody can have made a more impressive first start than Ollie Griffiths for the Dragons against Ulster at Rodney Parade on Sunday afternoon.
After nine minutes off the bench against the Warriors and another eight against Treviso, the back row forward went the full distance against Ulster without looking the least bit out of place.
The same could be said of Cian Kelleher, a 21-year-old Dubliner who, like Griffiths, lasted the course on his full debut for Leinster when they came from behind against the Scarlets to end the Welsh region's ten-match winning streak.
While Gary Ringrose became a Leinster regular at 20 with so many team-mates on Rugby World Cup duty, other backs of the same age have been busy making a mark, like Ospreys' wing Dafydd Howells and his Dragons' counterpart Ashton Hewitt.
At 21, Jack O'Donoghue has made a real impression in the Munster back row. Ultan Dillane, born in France but reared in his mother's native Kerry, is doing likewise at the same age in the second row for Connacht.
A fifth straight home win, this time over Treviso, enabled Connacht to take full advantage of the Scarlets' narrow loss in Dublin and go clear at the top with Dillane the youngest member of their starting XV.
For their next domestic engagement, Connacht will move down the road for a clash with Munster, the neighbours having climbed up to second place one point behind on the strength of their win over Edinburgh at BT Murrayfield.
By the time they get to Thomond Park on November 28, Connacht will have made another piece of history, in keeping with their status as Guinness PRO12 leaders. They will never have taken off on a longer mission than the one awaiting them in the opening round of the European Challenge Cup on Saturday.
The tie, the first of its kind to be staged in Russia, has taken them some 2,000 miles to Krasnoyarsk in Siberia for a crack at new opponents, Enisei-STM, whose stadium has room for more than 20,000.
Since the creation of its Celtic League forerunner in 2001, PRO12 teams have won Europe's premier prize five times, thanks to Munster's double and Leinster's treble. The honour of opening this season's Guinness PRO12 challenge falls to Ulster followed a couple of hours later by the Warriors.
Both will be breaking new ground - Ulster at Oyonnax, the Glaswegians in Paris against Racing. Apart from losing heavily to Toulon in recent seasons, both know what it takes to win in France - Ulster at Montpellier and Castres, the Warriors at Montpellier and Toulouse.
Munster are next up on Saturday afternoon in the one all-Guinness PRO12 tie of the opening round, against Treviso at Thomond Park. The Scarlets are at Northampton and the last time they were in that part of the East Midlands, they responded with one of their best wins anytime anywhere - four tries adding up to five points.
The other two of the Guinness PRO12's six contenders go into action on Sunday against Aviva Premiership opponents - Leinster against Wasps at the RDS Arena followed by Ospreys against Exeter Chiefs in Swansea.
Leinster have not lost in the first round since London Irish won at the RDS Arena six years ago which just happened to be the last time Ospreys got as far as the quarter-finals. They beat Leicester Tigers and Clermont Auvergne in the pool competition only to feel very hard done by at losing by a single point to Biarritz in San Sebastian.
How the Guinness PRO12 table stood after seven rounds last season:
1 Ospreys 30 pts
2 Warriors 27 pts
3 Ulster 26 pts
4 Munster 23 puts
5 Leinster 21 pts
6 Connacht 18 pts
7 Scarlets 18 puts
8 Edinburgh 11pts
9 Blues 8 pts
10 Dragons 7 pts
11 Zebre 5 pts
12 Treviso 1pt
After how it stands seven rounds into this season with the difference in brackets:
1 Connacht 28 pts (+ 10)
2 Munster 27 pts (+ 4)
3 Scarlets 26 pts (+ 8)
4 Leinster 23 pts (+ 2)
5 Ulster 22 pts (- 4)
6 Warriors 22pts (- 5)
7 Edinburgh 18 pts (+ 7)
8 Ospreys 11 pts (- 19)
9 Dragons 10 pts (+ 3)
10 Zebre 9 pts (+ 4)
11 Blues 9 pts (+ 1)
12 Treviso 4 pts (+ 3)
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