Pep Guardiola praised John Stones and Kevin De Bruyne after Manchester City opened their Champions League campaign with an emphatic 4-0 win at Feyenoord.Defender Stones headed two goals, including the opener in the second minute, while playmaker De Bruyne delivered another passing masterclass in an outstanding team performance at De Kuip.Strike pair Sergio Aguero and Gabriel Jesus were also on target as City ran the Dutch champions ragged.Manager Guardiola said of Stones: "There is no doubt about his quality. His two goals were so important."John knows what is the gap and where he has to improve, defending the duels, but he's so young and he is able to achieve."When he does, he will become an exceptional central defender."De Bruyne, who also impressed in last week's 5-0 thrashing of Liverpool, was the leading light of a brilliant midfield.Guardiola said: "Kevin is one of the best players I've ever seen in my life in terms of he can make absolutely everything."He's a top, top quality player. We are so proud and so happy he's with us."City are now already in a strong position in Group F ahead of back-to-back home games against Shakhtar Donetsk and Napoli.Asked if it was the perfect start, Guardiola said: "Of course. I said yesterday it's important to play good."I'm proud that we have scored nine goals in two games when we've had a lot of problems in that (area). Of course to score two early goals was so important."Three points are very important to start the group stage. Last season we were not able to win one game away. That's why if you want to make a step forward you have to do this."Stones also paid tribute to De Bruyne, whose contributions included a perfect cross for the England international's second goal.Stones told BT Sport: "I don't get on the scoresheet too much but I'm trying to bring more goals to my game."I'm just happy that I could help tonight. When the delivery's so good. Kevin kind of puts it on a plate for you. "I keep learning off the players like Kevin. Even though we don't play in the same position we're always training together and it's only going to make us better players."The game was effectively over inside the opening 25 minutes as City raced into a 3-0 lead.It was a tough reintroduction to the Champions League after a 15-year absence for Feyenoord and manager Giovanni van Bronkhorst admitted his side were outplayed.The former Arsenal player said: "I said they are a very good team, with a lot of qualities and speed - everything to be a top team. We weren't ready for them."We started not good. If you concede in the first two minutes and the second after nine minutes - that was a big blow. We couldn't get into the game."Maybe we were a bit anxious, nervous - the first time for a lot of players at this level. You could see the difference and the difference was too big."