The Red Devils recovered from two goals behind to lead 3-2 in the English capital, and the visitors were seemingly heading for all three points, with Chelsea trailing heading into the final exchanges.
However, Cole Palmer levelled from the penalty spot in the 10th minute of added time at the end of the 90 before completing his hat-trick with a deflected effort less than a minute later, as Mauricio Pochettino's side put on a late show to triumph in incredible circumstances.
Ten Hag has admitted that his side «made the wrong decisions» in the latter stages, but he questioned the award of Chelsea's second penalty of the match.
«Yes we started poor, kicking the ball away and defending poorly. But you saw we were dominating the game and it was brilliant how we played — we deserved to win the game,» Ten Hag told TNT Sports.
Ten Hag pleased with overall performance«But, you cannot give it away like we did and we have to manage this game better. It is a team performance, you can point to one of the players but it is about team performance.
»When it gets chaotic you have to deal with it as a team and we made the wrong decisions and we didn't help out as a team. Out of possession we made bad decision — a lack of concentration.
«Also, I think lucky at the end with the penalty situation, questionable and very soft but we have to do better.
»Definitely a setback and now we have to deal with this and get up — we are resilient and you have seen that today. The quality of our football is really high, but football is about results and you have to bring it over time."
Fernande Read on sportsmole.co.uk