There's disappointment at not scoring - but Oh insists he's grown in stature since moving to Celtic.
The South Korean international appeared form the bench in a 2-2 friendly draw with Colombia last week, and is in line for another cap against Colombia. He's netted three times for Ange Postecoglou's side since moving to the Premiership from Suwon Bluewings in January, and he says he took his confidence from Parkhead back home.
He is competing with Cho Gue-Sung - who Celtic tried to sign in January - and Hwang Ui-Jo for the chance to star in attack alongside Son Heung-Min. And despite being left less than impressed with his international display against Colombia, Oh tells Simin 119 : "It's been a long time since I made my A-match debut in an exhibition match against Iceland in November last year. It was an honour to play in front of so many fans. It was hard to adjust to jet lag at first. I think we showed a disappointing performance. I'm very disappointed with myself.
"I always imagined myself playing with my brothers while watching them from the sidelines at the Qatar World Cup. I'll keep the jersey from today's (Friday's) trial for the rest of my life."
"The Hyeongyu Oh of Celtic has become stronger than the Hyeongyu Oh of Suwon Samseong. My performance at Celtic came out as confidence in the national team.
"I faced a lot of physical European defenders. I feel that I have become stronger by not avoiding them and facing them stronger, I think I am stronger and more aggressive in the box than Cho Gue-sung and Hwang Eui-jo."
