Christian Eriksen felt Tottenham allowed Ajax to dominate the early stages of the first leg of their Champions League semifinal as the Eredivisie leader claimed a 1-0 advantage.
Ajax, which knocked out holder Real Madrid and Juventus in the previous two rounds, took control from the start and led through Donny van de Beek's 15th-minute strike.
Danny Rose then nearly sliced into his own net and Van de Beek was denied a second by Hugo Lloris' leg before the enforced introduction of Moussa Sissoko - on for Jan Vertonghen after he was unable to continue following a blow to the nose just after the half-hour mark - finally stopped Ajax's midfield controlling proceedings.
"I think first 20 minutes of the game, we were just ball-watchers," Eriksen told BT Sport after losing to his former club.
"Against a team that likes possession, it's a no-go. We need to change it up a lot for the next game.
"We made them look a lot better. It's a good side but I think we helped them on their way to give them their feet. They could control things, which was our fault.
"Second half was different. We played more direct and hurt them a bit more."
Though it eventually stopped Ajax from totally dominating, Spurs was unable to muster much in an attacking sense and Dele Alli's volley straight at Andre Onana in the second half was its only shot on target, while the post denied David Neres a second goal for the Dutch side with 12 minutes remaining.
Tottenham will get Son Heung-min back from suspension for the return leg in Amsterdam next Wednesday, when Eriksen expects to see a much-improved display from Mauricio Pochettino's men.
"Nobody wanted to play the first half the way we did - everyone felt disappointed we didn't compete at the level we know we can," the Denmark international added.
"We know we needed to change and we did. We still lost but we were better second half.
"We were lucky they hit the post because 2-0 would have been a different game for us next week. We need to change how we played a lot and hopefully we can turn things around in Amsterdam."
Van de Beek, meanwhile, was impressed with the way Ajax attacked in the early stages in north London but acknowledged Spurs' tactical switch from a back three to a four caused them issues.
"I think it was an important moment for us - first 30 minutes, we played really good," the Ajax midfielder said.
"After that Tottenham changed something and we had problems with that but I think 1-0, it's okay. Next week we have to finish it at home.
"The beginning was good but after we played not what we can. But we win and we have to make a good plan for next week."