The 25-year-old backrow forward -- labelled "a great dude on and off the pitch" by teammate James Lowe -- said it had been special to skipper Ireland for the first time in Sunday's Six Nations 36-0 hammering of Italy.
A very different character to former skipper Johnny Sexton and to the present incumbent Peter O'Mahony, it is he and not James Ryan -- for long seen as the heir -- who looks to be the captain in the long term.
Indeed the injured O'Mahony, 34, was said by head coach Andy Farrell to be extremely nervous at Doris replacing him for the Italy game -- though it was expressed in more colourful terms by the Englishman.
For Lowe it was as if Doris was to the manor born for the role.
"His speech before the game was outstanding, to the point, emotional, direct, it was like he’s done it before," said Lowe.
"He took it all in his stride."
It was all the more creditable as Doris spoke openly last year of being uncomfortable at times with the spotlight being on him in what he nevertheless called his "dream job."
"It does add a bit of pressure and awareness that there's more eyes on me; sort of 'How do I deal with this?'" he told website 42.ie.
"I think everyone has struggles, insecurities, worries and anxieties; the more we can talk about them and get them off our chests the better."
'WORRIES IN THE FUTURE'
Doris, who was born and brought up in the picturesque county of Mayo in the west of Ireland -- so rural there were just two boys in the class at school, said for years he would bottle up his feelings.
Doing that gave him an aura of calm, according to father Chris and mum Rachel, though he admits this encouraged him as a youngster to deal with being sad on his own.
"Personally, I wasn't very good at it when I was younger," he told 42.ie.
"Both my parents are psychotherapists, so it was encouraged quite a lot, but I wasn't good at it at all.
"It was a bit of a running theme that whenever I was asked I'd just say: 'I'm fine, I'm fine' and not give much more than that."
As Doris -- who with a friend has set up a clothing business making "minimalist garments" -- has matured, coming to terms with how bad he is feeling and expressing that has become easier.
"It's only the last few years that I've gotten better at talking about these sort of things," said Doris, who undergoes a therapy session every week.
"I'm fortunate that with my parents they're very good at dealing with that sort of stuff.
"It's comforting, but it still can be uncomfortable having discussions with those sort of things."
Doris -- who shares a house with Leinster and Ireland teammates Ronan Kelleher and Hugo Keenan -- has also not held back over the thorny issue of concussion.
His first experience of Test rugby in 2020 against Scotland in the Six Nations lasted just four minutes as he suffered a concussion.
He took the bold step of voluntarily sitting out the 2021 tournament due to concussion symptoms and in what he said was a "weird and uncertain period" went to a consultant in London to get checked out.
He was called "an inspiration" by former Ireland wing Tommy Bowe, "as it is hard when you are competing vigorously with someone for your position. You don’t want to give them a chance."
For Doris it is an investment in the future.
"I have always got those base lines to look back to, if there are worries in the future," said Doris, who has worn a scrum cap ever since his return.
"I'm glad I did it, definitely a tough decision, but I'm grateful I did and grateful I'm able to play again."
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