Zinedine Zidane held his hands up and accepted his half-time tinkering may have cost Real Madrid in their 1-1 draw at home to Real Sociedad on Monday.
Madrid were the more threatening of the teams in the first half at Estadio Alfredo Di Stefano, with Mariano Diaz hitting the crossbar from close range in a lucky escape for the visitors.
But, seemingly unhappy with his team's performance, Zidane altered his setup at the interval to go with a back three, only for Portu to ghost in at the back post to head in a Nacho Monreal cross in the 55th minute.
Zidane reverted to a back four soon after and eventually Madrid got their equaliser in the 89th minute through substitute Vinicius Junior.
But the Frenchman seemingly felt his half-time changes may have backfired.
Speaking to reporters after the game, Zidane said: "I changed it [at half-time] because I wasn't happy with our pressing.
"It was those 10-15 minutes and we changed it again and we were better playing a 4-3-3. Our substitutes did well after coming on."
Zidane was then asked again if he felt he made a mistake with his initial tweaks, to which he replied: "If you've asked me, and that's now three times, then yes, maybe.
"We had to change things because, after an hour, the team was a bit tired. Sometimes we have to change things. In the end, you try to find things to change the dynamic."
While Vinicius' late equaliser likely prevented Madrid from suffering a massive psychological blow ahead of a potentially pivotal derby clash with Atletico Madrid at the weekend, in the grand scheme of the title race it did little to improve their standing.
Either way, the pressure on Madrid going into the weekend is greater than if they had beaten La Real, as they stay five points behind the leaders having played a game more, yet Zidane insists Monday's result changes nothing.
"We have to remain calm," Zidane added. "We had a good game and we had three or four chances [to score].
"Patience, calm and rest. We were up against a team that creates chances against you. We have to carry on.
"It doesn't change the way we go into the derby. We have to go there to have a great game."