Motherwell goalkeeper Trevor Carson and Norwich full-back Jamal Lewis were handed their first Northern Ireland caps in Saturday's friendly against South Korea.
Kilmarnock's Jordan Jones was handed his first international start in a team that also featured veteran defenders Gareth McAuley and Aaron Hughes, while the uncapped trio of Conor Hazard, Paul Smyth and Shayne Lavery were among the substitutes.
Both of South Korea's Premier League players, Son Heung-min and Ki Sung-yueng, were in the visitors' starting line-up.
Carson was beaten from the first attempt on his goal in the seventh minute.
Park Joo-ho scooped a pass over the top of the Northern Irish defence and Kwon Chang-hoon came in off the flank, took a touch and slotted home.
The visitors nearly added a second shortly after but Carson was equal to Son's near-post effort from the left.
South Korea's lead lasted just 14 minutes as the hosts levelled with a set-piece special.
George Saville and Jamie Ward both ran away from a 25-yard free-kick and Oliver Norwood slid a pass to the side of the wall to the latter, whose cross was turned into the net by visiting defender Kim Min-jae.
It remained 1-1 at the interval with neither goalkeeper truly tested in the latter half of the opening period.
O'Neill had already been forced into an enforced change during the first half as Aaron Hughes, winning his 110th cap on the eve of the 20th anniversary of his debut, came off for Conor McLaughlin due to injury.
South Korea looked the more likely side to get the next goal as they went close with a series of deflected efforts.
O'Neill switched to a 4-4-2 by bringing on Conor Washington and Liam Boyce, and he then called for Watford's Craig Cathcart to replace Jonny Evans.
Debutant Paul Smyth needed just four minutes to deliver on Michael O'Neill's assertion that "the future starts today" with a late winner in Northern Ireland's 2-1 victory over South Korea.
QPR winger Smyth, who played 90 minutes for the Under-21s against Spain on Thursday, became the first Northern Irishman in 17 years to score on his international bow by firing home four minutes from time at Windsor Park.
The South Koreans had gone ahead early on through Kwon Chang-hoon but levelled when an ingenious free-kick routine led to Kim Min-jae scoring an own goal, with Smyth then stepping off the bench to help the Northern Irish move on from their World Cup play-off heartache.
O'Neill was quick to praise his super-sub Smyth at the post-match press conference.
The boss said: "It's fabulous for the boy. The intention was always to have him in, we didn't name him in the original squad because it's too complicated.
"With the 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, that's what we intended to do.
"He loved it, you could just see. His enthusiasm for the game is infectious, the boys love him.
"It was great for him, he's a player with a big future, but he has to work hard, he knows that himself.
"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."