Sexton -- Ireland's Captain Marvel
As the 38-year-old fly-half walked disconsolately round the Stade de France following the 28-24 loss to New Zealand on Saturday, accompanied by his adoring son Luca, his extraordinary set of accomplishments were probably far from his mind.
Sexton was 2018 World Player of the Year, as well as a pivotal figure in two Six Nations Grand Slams in 2018 and 2023, a historic series win over the All Blacks in New Zealand and Leinster's four European Cup victories.
He retires as both the Six Nations and his country's all-time points scorer and -- perhaps one he won't put near the top of the list -- at 38 years and 58 days he became the oldest player to represent Ireland when he started against Romania in September.
"Very, very simply he is the player in Irish rugby history who has had the most impact on the team they have played with and led," MacNeill said on Sunday. "No one else, no one else."
The 37-times capped MacNeill, who also played three Tests for the British and Irish Lions on the 1983 tour of New Zealand, said Sexton's captaincy over the past four years set him apart.
"Ciaran Fitzgerald was a great captain," said MacNeill of the man he played under when they won the 1982 and 1985 Triple Crowns.
"Willie John McBride was a great captain, Fergus Slattery was a great captain but Johnny is the best of them all."
The scars of Saturday's defeat will take a long time to heal but once they do Sexton should take pleasure in reflecting on how highly regarded he is.
For Ireland head coach Andy Farrell there is no doubt where Sexton sits in the pantheon of Irish rugby players: "The greatest".
For Sexton's long-time teammate and close friend Peter O'Mahony -- another who at 34 may well now hang up his Test boots -- he represents much more than just a player.
"He has changed rugby, changed Irish rugby, obviously for the better," said O'Mahony.
"He teaches people what it is like to be a professional, what it is like to be a proper Irishman."
'Mental animals'
Saturday's loss ended Sexton's hopes of emulating his fellow fly-half Jonny Wilkinson in achieving the Six Nations Grand Slam and World Cup in the same year -- the Englishman pulled off that feat in 2003.
For Wilkinson's 2003 teammate and now Ireland's attack coach, Mike Catt, Sexton reminds him of the England legend.
"They're both obsessive," Catt said back in March. "They're just completely different mental animals.
"They're so in the moment, they're so in the game. Everything means a hell of a lot."
The South Africa-born coach said the two also brought a feeling of reassurance to their teammates.
"When you stand next to a Jonny Wilkinson or a Johnny Sexton, inside or outside of him, you feel pretty special," said Catt.
Sexton's competitiveness for some over-stepped the mark on occasions, as he confronted referees or bawled out teammates.
"When he is negative and giving out to others it is not what a team needs," former Ireland fly-half Tony Ward told AFP.
"Not everybody has the same personality as him."
Nevertheless it was this drive and competitive spirit that produced results for Sexton personally and the teams he played for -- leadership came naturally to him.
"He is an unbelievably competitive guy who does not like losing and I think that is why some people love him and some hate him," former Ireland prop Marcus Horan told AFP.
Horan says Sexton's stoicism also came from self-criticism as you "won't get any worse critic than him on himself".
"It is very easy to bounce back from tough stuff but there is that resilience in him when successful to come back and go again," said the 67-times capped Horan.
"I admire that in him particularly."
If Sexton needs any help in rebounding from the despair of how it all ended then Luca, who he often cited in press conferences, is the solution if Sexton junior's comment after the match was anything to go by.
"You're still the best, Dad."