It will be hard to escape them if Sexton at 38 lifts the Webb Ellis trophy on October 28th to become the oldest player to win the Rugby World Cup.
At 43, Brady holds the record for the oldest player to win a Super Bowl - one of seven he won.
Sexton was at one stage more in awe of New Zealand lock Brad Thorn who aged 36 lifted the World Cup in 2011 - the oldest man to do so.
However, the arrival of former England head coach and professed NFL devotee Stuart Lancaster at Sexton's club Leinster in 2016 changed all that.
"Stuart has got me obsessed with Tom Brady," said a then 32-year-old Sexton in February 2018.
"I didn't know Brady myself. I didn't watch any American football but he is the most successful quarterback in the history of the NFL."
The canny Lancaster struck the right chord.
There is nothing that motivates Sexton more than making history or being the best at something - though the fly-half's long-suffering wife Laura would not have been pleased.
"Stuart has got me convinced I'm going to play 'til I'm 40 and my wife is going mad!" said Sexton.
"I'm reading up on him (Brady) and trying to figure out how to prolong my career as long as possible."
Lancaster said having got to know Sexton it was clear how much the two sporting maestros had in common.
"I can see the comparison," said Lancaster in 2018. "Honestly, I can.
When I started watching the (New England) Patriots and understanding how they went to five Super Bowls and Tom Brady is the quarterback who has done it, I could see it.
"I kept finding clips and sending them to Johnny."
'The Tom Brady of the IRFU'
Sexton certainly read the right books about prolonging his career as he prepares to lead the team out for Saturday's quarter-final with the All Blacks.
He has, though, eased Laura's angst by saying 40 is beyond him and once the final whistle goes for the Irish in this tournament, it may not be the pipe and slippers moment but it will be time to hang up his boots.
Sexton has even used Brady's words to gee up his Leinster teammates typically after a major victory - the European Champions Cup in 2018.
"Johnny addressed us in the dressing room and cited Tom Brady, who after winning a Super Bowl was looking towards winning the next one, not reflecting the one just gone," recounted hooker James Tracy.
"It was all about legacy and how many we win."
Sexton has reminded others of Brady - as in being the undisputed number one for Ireland and staying there.
Billy Burns, Ross Byrne, Joey Carbery, Jack Carty and Ian Madigan have all tried their hand and fallen by the wayside as Sexton has maintained his high standards.
"Tens, in terms of key decision-makers, they're your quarterback - like Tom Brady, people have been writing him off for what, the last six seasons, but he keeps proving people wrong and coming back and he's what, 42 now?" said Leinster director of rugby Leo Cullen in 2020.
"I think Johnny sees himself in that mode. It's the ability to think."
For Sexton's former Leinster and Ireland teammate Jamie Heaslip, Brady sprang to mind when asked whether the Irish captain was under threat before the Six Nations last year.
"Johnny is the GOAT. He's not going anywhere," said Heaslip.
"He's the Tom Brady of the IRFU right now and he's not going to give up that jersey.
"He's head and shoulders above everyone else right now."
Sexton has not let Heaslip down. A Hail Mary or two - the prayer, not the pass - could see his final dream fulfilled in fairytale Brady fashion.
