Goals from Kevin De Bruyne, Kelechi Iheanacho, Raheem Sterling and Ilkay Gundogan secured the hosts all three points and ensured they continued their 100% record so far this campaign.
“We weren’t at it today,” explained Cook.
“You have to be when you play sides like this and players like that, but we weren’t and we got punished.
“The first two goals were soft. It was obviously a great free-kick but we gave the ball away cheaply and then the foul.
“For the second, they countered us on the break from our own free-kick – so that is hard to take.
“But we’ve been beaten 4-0 and it hurts a lot. We need to bounce straight back to winning ways.”
Eddie Howe’s men will have the chance to do just that on Tuesday night when they host Preston North End in the EFL Cup.
And despite today’s result, Cook was able to highlight the Cherries’ endeavour as a positive factor.
“The only positive, really, is that we never gave up,” he continued.
“In parts we passed the ball well and caused them problems, particularly Josh King in the first half getting in behind. Apart from that there aren’t many positives to take.
“But they are the best team in the league. They’ve got the best manager arguably in the world, so it was always going to be a very, very tough day for us."
