Robert Page celebrated Wales reaching the last 16 of Euro 2020 after sending on Kieffer Moore against Italy and telling the substitute to "jump with no arms".
Wales held on to second spot in Group A despite losing 1-0 in Rome, finishing above Switzerland – who beat Turkey 3-1 in Baku – on goal difference.
But Wales' five-goal advantage over Switzerland at kick-off was in danger of being wiped out when Ethan Ampadu was dismissed after 55 minutes.
Ampadu was shown a straight red card for a late challenge on Federico Bernardeschi, and interim manager Page turned to Moore as an attacking option to keep the ball away from an overworked Wales defence.
The 6ft 5in Cardiff striker had been left on the bench with Page aware that a second booking in the tournament would rule him out of a last-16 tie.
"I went with my heart for the last half-an-hour and got Kieffer on the pitch," Page said after Wales had lost to Matteo Pessina's first-half volley.
"Otherwise we would have been camped on the edge of our box.
"To do that against a very good Italian team they would have broke us down again and it could have been two or three.
"Kieffer is one of those players that unfortunately could accidentally get a booking. He understood my concern.
"I asked him to jump with no arms and he did. Watching him jump was hysterical."
Moore scored Wales' first goal of the tournament in the 1-1 draw against Switzerland and is integral to their style of play with his size, strength and hold-up ability.
"I had some tough decisions before the game," said Page, whose side will now head to Amsterdam to play either Denmark, Finland or Russia in the round of 16.
"My heart was telling me to continue the momentum against Turkey and keep going.
"But there was a risk element with the three lads on bookings. There was a strong probability – a 95 per cent chance – that we would have gone through anyway, so I put them on the bench.
"They understood my concern and agreed with the decision."
Wales became the smallest nation in terms of population to reach the semi-finals of the European Championship in France five years ago.
Asked how Wales had managed to make the last 16 again with such a small population, Page replied: "Don't underestimate the character of a Welshman.
"It's phenomenal what that changing room has got in there. I'm absolutely bursting with pride.
"I can't speak highly enough of them, they got the job done to finish second."