City fought back from a 1-0 deficit at half-time to level within seconds of the restart, Doku cutting inside Vladimir Coufal with excellent footwork and sliding beyond Alphonse Areola for his first goal for City.
All that had looked less likely when James Ward-Prowse headed in from Coufal’s cross in the first half to give West Ham a deserved lead and put them on course to overtake Guardiola’s side in the league.
The manager said he had not expected such an immediate impact from the 21-year-old Doku, who cost £55million to sign from the Ligue 1 side in the final week of the transfer window, and feared there was a shyness to his performance when he made his debut against Fulham before the international break.
Guardiola watched that game remotely from Barcelona whilst he recovered from back surgery, but since returning to Manchester has been impressed by the progress the Belgium international has made following the 5-1 win against Marco Silva’s side.
“I was in Barcelona, I had the feeling that he played a little bit shy (against Fulham),” he said. “He’d just arrived, had two or three days training, with a team that won the Treble. Maybe he was a little bit in this way.
“But today, no. (I said) use your quality as a winger. One against one, one against two; go. If you don’t have the feeling, pass back to Josko (Gvardiol) and play again.
“Today was from the first minute incredible, aggressive, great determination, arrived many times to the byline. Many, may good things he’s done. Really, really pleased. We thought the quality was there and today he started to prove it.
“When you buy a young player like him for many years (contract), we have to be patient. We cannot expect, I didn’t expect the second game for City to play like he did today. The way he played today, I don’t remember from a long time ago something like that.
“There are processes that he has to learn. Always we are there to help him. At Manchester City, every player has to be (himself). All the players here have a lot of quality.”
City have won all five of their league games this season as they seek an unprecedented fourth consecutive league title.
They were placed under pressure by West Ham for a period in the second half as David Moyes’ side went close through Michail Antonio, Emerson and Kurt Zouma, with Ederson in goal producing a string of fine saves.
“I would say West Ham had more chances in the second half than the first,” said Guardiola. “We created against a team that defends so deep and really, really well. We created a lot of chances in the 90 minutes.
“I’m so proud of the team. It’s great win for us, for the problems (injuries) we have in the squad. It doesn’t matter, the guys always respond well.
“We spoke at half-time, don’t be affected by the result because you’re playing really, really good in the first half. In the second half we were lucky to start and score a goal immediately, we had to be patient then and we had our chances, they had their chances. But really, really good in the way we played.”
Moyes reflected on a game in which his team ran the European champions close but ultimately did not have enough to avoid going down to their first defeat of the season.
“Our other games have had a lot similarities,” he said. “Chelsea missed a penalty kick, then Mick breaks through and scores to make it 2-1. Small margins in football. To be fair, the early season ones have gone for us.
“Today we played against a top team and we’ve done an OK job. Bits l liked, bits of it I didn’t like. But overall I have to say the players did a brilliant job.
“We tried to make it difficult, we always do against City. I think you have to be really clinical and also really clinical defensively as well. You can’t afford to make many mistakes.
“I thought the first goal came at a bad time. I thought their second goal was a mistake and we should have dealt with that much better. It changed the game really at that point.”