'The Tullow Tank' has, since his emergence at provincial level back in 2008, become one of Ireland's most beloved sportspeople. He embodies what we perceive to be great about Irish sport; pace, freakish aggression, and farmer strength.
The IRB's Rugby News Service once described O'Brien as 'a rampaging ball of destruction', selling him short by a considerable distance. We've all seen his barn-storming runs and brutally forceful carries, and his crucial tries for both club and country. But here are seven of SOB7's most shamefully unseen or underappreciated moments from a glorious career.
1) His random GAA sightings
— Fighting Cocks GFC (@FightingCocksIE) June 2, 2014
While Ireland arrived in Argentina for their summer tour in 2014, O'Brien was playing Division 5 Gaelic football in his native Carlow.
FYI, as per the Irish Independent at the time, the Fighting Cocks won 3-6 to 0-11 on O'Brien's return to the fold.
2) The ad that the IRFU should have used for their 2023 Rugby World Cup bid
There's something oddly serene about watching O'Brien frolic through a meadow, push bales and fling logs. It might spring scenes reminiscent of an Owen Colgan video in which he's warning us about ISIS, but it would have made an ideal proposal video in Ireland's bid to host the 2023 Rugby World Cup.
3) His incredible pre-season training regime
Pre preseason is underway! pic.twitter.com/W485kqIUQ1
— Sean O' Brien (@SeanOBrien1987) June 26, 2014
Ah, come off it.
4) His appreciation for Katie Taylor's incredible training regime
how are you fixed to drive a few stakes on the farm in next few weeks??
— Sean O' Brien (@SeanOBrien1987) February 2, 2017
If you search Katie Taylor and Seán O'Brien's names together on Twitter, you'll find a strange longing from Irish sports fans circa 2012 for the pair to procreate and produce an Irish super-athlete. We're not even joking.
5) The time he cleared an entire French ruck on his own
Rumour has it that O'Brien is known as 'Le Démon Spud' in southern France.
6) The time he took names against the English
In Northampton, he's referred to only as 'He Who Must Not Be Named'.
7) His willingness to teach Jordi Murphy about farming
Former Blackrock student Jordi Murphy knew nothing of the pain of calving or indeed Mastitis, but O'Brien took the time out of his day to educate his fellow Leinster back row about farming struggles. Balls understands Murphy later returned the favour, and introduced Seanie to The Greenery in Donnybrook.