Vertonghen admitted there were no excuses.
"Everybody was fit," he said.
"Many of us have had international matches but we play European games as well so that was not a problem.
"It is very disappointing. We came into the game very motivated to get a good result. But if you concede a goal after 15 seconds it is a bad thing.
"It is our own fault. Manchester City score a lot of goals at home but we gave three or four of them away too easily.
"I would just love to have the chance of playing this game again next week because we are better team than that."
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