Barcelona coach Hansi Flick said he is to blame after wholesale changes resulted in a 4-2 loss at Osasuna on Saturday as his side's seven-game winning run in LaLiga was ended.
Lamine Yamal and Raphinha were among five players rested after the midweek win over Getafe as Barça tasted defeat in the league for the first time this season.
"We had a lot of changes in the team and this is maybe one reason for [the performance], but it was necessary," Flick said in his post-game news conference.
"We had so many matches and a lot of players had played so many minutes. I had to take care, this is my responsibility. If you want to blame someone for this defeat, blame me."
Barça would have matched the club record of eight successive wins at the start of a LaLiga campaign by winning at El Sadar, but they fell behind to Ante Budimir's header in the 18th minute.
Bryan Zaragoza rounded goalkeeper Iñaki Peña, filling in for the injured Marc-André ter Stegen, to double Osasuna's advantage before half-time, but Pau Víctor's first Barça goal got the away side back into the game after the break.
However, Barça's hopes of a comeback ended when Budimir scored his second of the night from the penalty spot after being fouled by Sergi Domínguez, the 19-year-old centre-back who was one of the five players to come into the side.
Abel Bretones' long-range strike then made it 4-1 before Yamal added a late consolation with a stunning drive from the edge of the box, his fifth goal of the campaign.
"In the second half we tried to get a better result, we make the 2-1 and we have some chances, but the penalty killed us," Flick added.
"I will analyse the match and maybe will see some things about the decisions of the referee, he was not everything 100% right. But we have to accept it.
"We will go on. I really think positive about this team. Everyone is on the right way and we will show it in the next two matches against Young Boys and [Alavés]."
Flick insisted he would make the same changes again given the chance, pointing out that injuries have prevented him from rotating more during his first few months as Barça coach.
Dani Olmo, Frenkie de Jong, Gavi and Fermín López are all in line to return after the international break, but before then Barça must negotiate a Champions League game at home to Young Boys on Tuesday and a trip to Alavés in LaLiga next weekend.
"I had no other choice," Flick stressed when pressed on his changes. "If you see at the moment our team, we have three midfield players, plus we had one defender who is Eric [in midfield].
"Then we have [Marc] Casadó, we have Pedri and we have Pablo [Torre]. So, four players. And you have to think about what players are starting. This is not easy but we accept it.
"After the break in October, there are many players back. The situation is we have many injured players, but no excuses. We have to accept the defeat, it was not our best day.
"I am always looking forward and I am positive. We have to make our first win in the Champions League on Tuesday, because three points is very important.
"It won't be easy because Young Boys have a good team, a very fast team. We have to take care of that also, so we will see how we do it."
Despite the defeat, Barça's encouraging start to the season under Flick means they remain four points clear at the top of the table ahead of Sunday's Madrid derby, which sees Real Madrid and Atlético, second and third in the table before the weekend, meet at the Civitas Metropolitano.