Goals from Trent Alexander-Arnold (23), Mohamed Salah (30) and summer signing Darwin Nunez (23) helped Liverpool in the season's curtain-raiser at the King Power Stadium, with another new signing, Julian Alvarez (22), scoring City's only goal.
"There is no reason not to be confident," Guardiola told reporters. "No reason. What these guys have done, not just in the Premier League but the (domestic) cups and Europe (says it all)."
"I don't know what will happen this season but I'm sure I know these guys. I have no doubts for one second."
"Days ago we played against Bayern Munich and did a very good performance and against Liverpool we did very good things. I don't feel that we are far away."
Guardiola left Kalvin Phillips (26) on the bench in the Community Shield but said the England international, who was signed from Leeds United in a deal reportedly worth 45 million pounds ($54.81 million), will be gradually eased into the team.
"He has confidence - he's ready to play," Guardiola said. "He only arrived three weeks ago and we have Rodri, Bernardo Silva and Ilkay Gundogan who know our play already. But step by step he will get it. In many games he is going to help us."
Manchester City kick off their bid to win a third straight Premier League title with a trip to West Ham United on August 7th.
