Northern Ireland's Paul Smyth was described as a "small player" with a "huge heart" after scoring the winning goal against South Korea just four minutes into his international debut.
The 21-year-old clinched a 2-1 victory for Michael O'Neill's side with an 86th-minute strike at Windsor Park.
"It is fabulous for the boy," said O'Neill. "He loved it, you could see.
"His enthusiasm is infectious and the boys love him. He's a player with a big future, but he has to work hard."
Queens Park Rangers forward Smyth is the first Northern Irishman for 17 years to score on his international debut.
He had played for the full 90 minutes for the under-21 side against Spain on Thursday.
O'Neill said: "He's still very small, he's still very light but he's got a huge heart for the game and we're delighted with him."
South Korea had gone ahead early on through Kwon Chang-hoon, but the hosts levelled when an ingenious free-kick routine led to Kim Min-jae scoring an own goal.
Smyth then came off the bench to grab the winner and help Northern Ireland begin to move on from their World Cup play-off defeat by Switzerland.
"We were a bit rusty," said O'Neill. "Three or four of the team have not played much first-team football recently and sometimes that shows a little bit.
"But we dug in and scored a very good goal off a set-piece and that gave us a foothold and a bit of belief.
"After that we have as good as we got and it was great to go on and win the game - and the nature of how we won it was fabulous."
O'Neill said he had always planned to bring Smyth into the senior squad.
"We didn't name him in the original squad because it was too complicated," he said.
"With the under-21s playing Spain on Thursday we wanted his focus to be there. We didn't tell him he was coming in until after the game. That was the plan all along."