Julen Lopetegui has warned his Real Madrid side "have to improve in all facets" if they are to challenge Barcelona for the title in La Liga after seeing his side lose their first competitive fixture under his tenure.
The former Spain manager pulled no punches as he assessed his team after Wednesday's 4-2 extra-time defeat to city rivals Atletico Madrid in the Uefa Super Cup in Estonia.
Atleti's Saul Niguez and Koke struck in quick succession in the additional period at Tallinn's A Le Coq Arena following a 2-2 draw in normal time.
Real had been 2-1 up, with Karim Benzema cancelling out Diego Costa's first-minute opener and Sergio Ramos then converting a 63rd-minute penalty, before Costa netted his second of the contest to draw things level.
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"We had good game phases, but it was not enough," Lopetegui said in his post-match interview.
"We have to congratulate Atletico, I believe that they have won deservedly.
"We are not happy and the negative is that we have conceded four goals and this is not normal. This will have to be improved, without a doubt.
"We have to improve in all facets, we do not like when we make mistakes and we have to improve in everything, not only in individual errors.
"[It is a] feeling of frustration and sadness. But knowing that responsibility forces us to get up and try to improve and start the league as we want to start."
For Lopetegui, who succeeded Zinedine Zidane as manager after being controversially sacked by Spain on the eve of this summer's World Cup, it was a warning of what life is likely to be like at Real without club record goalscorer Cristiano Ronaldo, who joined Juventus this summer in a €100 million (Dh418.2m) deal.
The Spanish giants clinched a record-extending 13th title in Europe's top club competition in May with a 3-1 victory over Liverpool in the Kiev final, a competition they have now won in each of the past three years and four of the past five. Only one La Liga title has been won in that period, and they finished third last term – 17 points behind bitter rivals Barca.
When asked about Real's hunger having won the Champions League so many times, Lopetegui said: "We want to focus on the season without thinking about the last years and get the best out of the team.
"We want to get up now and think about the league, which makes us excited," added the Spaniard, whose first league fixture will be against Getafe on Sunday. "The team has won few La Ligas in recent seasons and we want to start well.
"They are not less hungry for having won the Champions League. They were hungry, eager, excited to win this title."
Atletico manager Diego Simeone, who was forced to watch from the stands while serving the third match of a four-game touchline ban imposed on him after his sending off in the Europa League semi-final against Arsenal last season, expressed his delight.
The Argentine said: "Happy, once again, we were able to respond very well in a final, especially in Europe.
"Today, we have to enjoy, no doubt. From tomorrow night, we will start thinking about the league, which is going to be a very hard season".
Simeone, who guided his side to the runners-up spot in La Liga last term as well as Europa League glory for a second time, are at Valencia on Monday.
He added: "More titles this season? Everyone knows me: Valencia."