The 20-year-old, who was deployed as a left-back despite being an attacking midfielder, opened the scoring for Man City in the 84th minute.
O’Riley has been a revelation since breaking into the first team earlier in the season, scoring four goals and providing two assists in his 14 games across all competitions.
City rejected advances from Chelsea in January and are reportedly set to tie the youngster down to a new long-term deal in the near future.
Speaking to the press after the game, Guardiola was full of praise for the youngster, admitting he is ‘so grateful’ to have him.
“He’s an attacking midfielder and when you play as a left back, you can arrive there,” Pep pointed out.
“He always is there. Look at Plymouth and Bournemouth. When you play full back you score, look at Josko before, now him.
“We are so grateful because he’s not a left-back. They have so many tall, strong players.When the take is good and you are tall you have a chance. They hit the post and then Stefan make a save.
“They make a good 10 minutes in the second half but then we work hard to find the goal.”