Under overcast conditions at Taunton, Pakistan captain Sarfaraz Ahmed looked especially pleased to have won the toss and put Australia in; Pakistan had left out their ace spinner Shadab Khan specifically for this eventuality. The joy would soon evaporate, however, as Australia put on 146 for the first wicket in 22 overs, looking well on track for a total above 350 on a pitch where the par score was at least 75 runs below that.
That they didn't manage to get there was thanks almost solely to one man, Amir needing to come up with career-best figures - including a first ever five-wicket haul in ODI cricket - to bowl Australia out for 307 in 49 overs. Given the impregnable position they had been in less than two hours earlier, it was an impressive passage of play for Pakistan, and a reminder of why Sarfaraz had opted to bowl first - this was what Pakistan had hoped would transpire for all 50 overs, not just the second half.
That Amir would need to fight something of a lone hand was evident in the first five overs, where despite the left-armer having conceded just three runs in his first three, Australia had raced to 27 in the opening 5. Shaheen Afridi, playing in place of Shadab, hadn't made the selectors look too bright with an opening two overs where he was much too short, far too predictable, and way too inaccurate to complement his colleague at the other end. Perhaps he, or indeed Hasan Ali who followed him, hadn't figured out the best strategy for the pitch - something Amir said he had sussed out as early as the first over.
"As soon as I bowled the first over, I got the idea it wasn't swinging, it was seaming," he told the PCB's official website. "So I was just floating the ball and making sure I put it in the right area instead of putting too much work onto it at the point of release. And the movement it generated came off the seam. It was just a matter of hitting the right areas on this wicket and I did that effectively.
"There's no doubt Australia batted well, but in the first 10-15 overs, we weren't able to pitch the ball up as consistently as we needed to. I think that might have been the difference between a score of 250-260, and the 300 plus they ended up getting."
The five-wicket haul means Amir is now the leading wicket-taker at the World Cup (10), a remarkable turnaround in form from just a few weeks ago. In the initial squad, named on April 18, Amir had been left out by Pakistan because his ability to strike at the top of the innings had deserted him. Before the first game of the World Cup, he had managed just five ODI wickets in the two years since the end of the 2017 Champions Trophy, and none in the first Powerplay for 17 months - 12 consecutive ODIs. It was his uncanny ability to keep the runscoring down at all stages of an innings, however, that saw him get the nod at the end. At Taunton, he was impressive by both metrics, conceding just thirty runs in ten overs even as Australia ran up a total of 307.
Even so, he acknowledged his personal glee was tempered significantly by the 41-run defeat, which leaves Pakistan precious little margin for error if they are to make it to the semi-finals.
"It would have been a lot more satiating if we'd won, of course," Amir admitted. "We have to win every single game now. We can't lose even one. We have to go into each match with a positive mindset, because pressure exists for every team, not just Pakistan. If we continue to play the positive cricket we played for parts of the Australia game, I'm sure we can win."