"You just don't know how bad it's going to be. It could have ended my career," Bairstow told Sky Sports' Ian Ward, as he recalled the horrific slip on a golf course last September that brought an abrupt end to the most extraordinary season of his career, and left him instead with a leg that was broken in three places, plus a dislocated ankle and associated ligament damage.
A less bloodyminded cricketer than Bairstow might not have even contemplated such a hard-fought comeback, let alone succeed in returning to action in time to take part in one of the most hotly anticipated Ashes series of recent memory. The fact that he did so as wicketkeeper, after the stunning impact of his batting replacement Harry Brook, was an extra burden.
At times in the series, it has visibly weighed him down, with a succession of missed chances behind the stumps leading to speculation about his place for this Test. But, after plucking an outstanding one-handed chance off Mitchell Marsh in Australia's first innings, he rode that confidence into a formidable display of power-hitting at the back-end of England's reply, with his ten fours and four sixes helping to extend their lead to a daunting 275.
"I've got nine pins, and a wire that goes through my ankle, and I've had nine months out," he said. "I'm still only 10 months post-operation right now. So when you speak to the surgeon and he says 'I'm surprised you're walking and running, never mind playing professional sport', I'm delighted to be where I'm at.
"There's times when there's aches and pains and people are saying you're limping, well, yeah, I am at times, because there's a lot going on in the ankle, and other bits that people won't understand. It's been a rollercoaster. There's been a lot that's happened in those nine months. And to come out and take the field again, with a group of boys that I care a heck of a lot about, is a special place for me to be."
Asked about his struggles behind the stumps, Bairstow acknowledged that his lack of playing time had been a massive factor.
"There's been a couple I've put down. I've not kept wicket for three years," he said. "I played a couple of games for Yorkshire, then straight into an Ashes series. I didn't bat against Ireland because the boys played unbelievably well. I'm delighted as to where I am. From a physical point of view, it's taken a heck of a lot of graft.
"But you know what I'm like, you know my personality. It's not for a lack of trying. I'm very, very proud of every time that I walk out and put on an England shirt, whether it be in a Test match or an ODI or a T20. I'm a proud, proud guy and it means a lot to me, and to get back and be available for selection for the Ashes is something that makes me immensely proud.
"I couldn't have done it without my friends and family, and all the support that they've given me throughout the winter. I'm just pleased to be playing. That's exactly what it's about. The people that have got your back, the people that are there through thick and thin.
"That dressing room is so solid," he said, gesturing at the England balcony. "We've got a special group of players in there, and a group of players that'll fight tooth and nail for each other, and we've seen over the last 12-18 months, the direction that we want to go as a group.
"I don't think that's changed throughout the series. Our approach has been questioned at times by you guys, but we've stuck to our guns all the way through. That's exactly how we played our cricket ever since Ben [Stokes] came in charge of the side, and that's what we're sticking by. We've not taken a backward step, no matter who we've come up against. Whether that's right or wrong, we'll continue to do that because, there's a bigger picture that's been spoken about, with the game of Test cricket."
On his tactics on the day, Bairstow acknowledged that his own experience of being a wicketkeeper had helped him to judge which deliveries he could safely steal a bye and get his partner James Anderson off strike, and added of his own hitting options with Australia's fielders set back on the rope: "When you're downwind, you've got to go up.
"With the squares as they are the moment, you've got to try and hit it as hard as you can across the square and let the rest happen. We're fortunate to play on good pitches and the outfield has been quick, so it's just a case of trying to pick the biggest gap and trying to hit it as hard as you can."
Speaking afterwards on Sky Sports, Nasser Hussain remarked that Bairstow had been "ticking" throughout his innings, and credited Stokes for reading the situation perfectly after lunch. Instead of declaring with England nine-down and Bairstow unbeaten on 49 from 50 balls, he trusted his team-mate to keep attacking a tiring Australian attack and building England's lead with the sort of statement innings that he tends to produce when he's got a point to prove.
"Everyone thinks that I play better when people go at me, it gets a bit tiresome to be honest with you," Bairstow insisted. "I've played a lot of cricket now and to be keep being told that you're rubbish. Well, if I was that was that rubbish. I wouldn't have played 94 games …
"I've been happy [with my form]," he added, obliquely referencing the controversy at Lord's where his stumping on the final day of the match opened the door for Australia's second victory. "There's been a couple of interesting dismissals during the series … but it's only a couple games ago that I got 70-odd, so it is what it is.
"That's part and parcel of the way that I want to play my cricket. want to go out and enjoy it. I want to go out and entertain. People will have comments on the way that I bat, they always have done. That'll carry on, but you can leave them to their comments, and I'll just keep on doing what I'll do in the middle."
On the Lord's controversy, Bairstow stated: "I don't have a view". However, he acknowledged he had been extra mindful of staying in his crease throughout his innings at Old Trafford. "I've done that all series since that happened," he added. "You've just got to be careful on those things, haven't you.
"It wasn't the way that I wanted to be out down at Lord's, but that's part and parcel. We've seen it on other occasions, and I've even heard about it now in club cricket. That's not necessarily what you want to be hearing about, when you're looking at young kids coming up. You play it tough, you play it fair, and on a different day, it doesn't happen but it is what it is."
Andrew Miller is UK editor of ESPNcricinfo. @miller_cricket