Nathan Lyon collected his baggy green cap from the umpire in mid-afternoon with figures of 0 for 27 from five overs and a glum look on his face. His most recent six balls had been taken for 10 runs by Hashim Amla, and it was no surprise when the captain Steven Smith chose to remove him from the attack.
Watching on from the outfield as the pacemen were rotated, Lyon must have pondered his situation. He had broken a lengthy wicket drought in the first innings, but the thought of a single victim in the course of five first-class innings can only have been the slightest consolation. A career tally of 214 Test wickets offered more robust reason for self-belief, but increasingly Lyon has seemed alone in keeping the faith. He is the team's most experienced player, and custodian of the team song. But somehow, unfairly, he had seemingly become expendable.
How close did he come to being dropped for this match entirely? About as close as it is possible. Steve O'Keefe, Lyon's New South Wales team-mate, would almost certainly have been chosen in his stead if not for the recurrence of a calf problem during the Sheffield Shield round played between Hobart and Adelaide. On local radio, the coach Darren Lehmann said as much: "Lyon was in because we couldn't select O'Keefe, he was injured beforehand."
Having made it narrowly to Adelaide, much of the talk leading into the match surrounded how Lyon could find himself making way for a fourth seamer in either Jackson Bird or Chadd Sayers. All despite Lyon's own fine record in Adelaide, and the absence of an allrounder making it vital to have someone capable of long spells. At a ceremony to name the players' viewing area after the loveable Barry "Nugget" Rees, Lyon prompted the guest of honour to nominate him as a favourite player. Laughs were had, of course, but Lyon was certainly in need of some love.
So close to being discarded despite being Australia's most prolific-ever offspinner, Lyon had to be pondering whether this still Adelaide night would be among his last in the national team. He has a captain in Steven Smith who does not share his predecessor Michael Clarke's dynamism when dealing with spin bowlers, and a coaching staff that oddly does not feature a full-time spin minder - South Africa's spinners have Claude Henderson on tour.
It is true that Lyon has been able to spend time this week with John Davison, his longtime mentor and trusted confidante. That has undoubtedly helped his technique, flight, shape and spin. "It hasn't been an emergency call," Lyon said. "Davo's been planning before the summer to come down to Adelaide. It's been great to have him around, he's someone I trust very highly and work great with him.
"He's one guy who is very handy to have in my corner. There's a bit of that [reassurance], but Davo also challenges me to try to get better and better each and every training session that we go into. He's just someone I can go to and say 'What do you think about this, this and this?' and he'll come back and say agree or disagree and we can have a conversation."
But he still needed to find a way to get himself into the game. After a brief flirtation with David Warner's medium pace after tea, Smith handed the ball back to Lyon. The dismissal of Amla in the interim helped Lyon, giving him a left-hander to size up in JP Duminy.
The following spell brought gradual improvement from Lyon, as he worked with variations in pace and spin. A major factor in the way he was able to get into the spell was a different level of pressure from the scoreboard, after Australia's batsmen finally produced something of substance after five matches of failures.
"It's always handy to have some runs on the board, and it's up there with the best innings by a nightwatchman that I've seen, so hats off to Usman," Lyon said. "It's been an exciting feel this week with a couple of debutants, we want to come out buzzing and prove to Australia that cricket's in good hands.
"I didn't feel under pressure to be honest. I know on the scorecards there's been no wickets in the columns but I feel like I've been bowling really well and being able to create chances. I haven't been feeling under pressure that much to be honest. I look at this as a young, exciting team and I've played 60 Test matches now and I've got a massive role in this team.
"It's not about being different it's about being there in a supporting role, taking a few of the younger guys under your wing and supporting them. I know how hard it is to play Test match cricket, and if someone in the team can lend that support on and off the field it's crucial. I know Mike Hussey was my mentor when I first came in, so if I can play my role with the young guys coming in I'm more than happy to do that."
The role to Duminy was to open up an end so that Smith could return to attacking with his pacemen under the Adelaide floodlight. A straighter, quicker delivery that skidded off the pitch did just that, beating Duminy's absent-minded flick across the line and knocking out off stump. Lyon's auxiliary role at this point was underlined when Smith withdrew him an over later to try tandem pace to Faf du Plessis, a decision rewarded with a sliced drive off Mitchell Starc and a tremendous catch by Pete Handscomb in the gully.
As stumps crept nearer, Smith returned the ball to Lyon's hands for a critical period. Temba Bavuma and Stephen Cook had the chance to forge through to the close and keep the dangerous Quinton de Kock safe from harm. But Bavuma's innings had grown skittish under pressure, from Starc in particular, and Lyon was able to exploit this by coaxing out a sweep, a top edge and a catch for Smith. Bavuma reviewed, somewhat oddly, but the HotSpot was clear.
This whole sequence showed how match circumstances, a hint of good fortune and a supportive Adelaide crowd make as much of a difference to Lyon as anything from the ball or the pitch. Against the nightwatchman Kyle Abbott he was masterful, working a tall man over with spin and bounce, before straightening one ideally for an lbw verdict.
De Kock was left to face the final few balls of the night, and for the first time all series it was Lyon who held the whip-hand. As the ball bit and spun past a groping bat, the crowd transfixed by the moment, it seemed difficult to imagine an Australian team without Lyon in it, when hours before the opposite felt true. How quickly things can change.

Daniel Brettig is an assistant editor at ESPNcricinfo. @danbrettig