Guardiola fielded an inexperienced side against a near full-strength Manchester United team and saw his team get narrowly beaten 1-0 thanks to a second half goal from Juan Mata.
However, despite defeat, the former Barcelona and Bayern Munich boss says that he was "proud" with the way his team played and said that young full-back Pablo Maffeo was "amazing".
"I am so proud of our performance, congratulations to United, but I am so proud of our young players and how we played," he told 'Sky Sports'.
"We had our chances, two or three on the counter…At that level, it's when you are more clinical with the last pass, but it's always difficult against United. We competed well".
He added: "They did a good job. (Pablo) Maffeo was amazing, fighting with (Marcus) Rashford and (Paul) Pogba and he won almost all the duels. I am so proud, we are happy.
"I want to try to win but that's competition. Next season we will try again and we have to try to focus on the next competitions".