Real Madrid manager Carlo Ancelotti was a relieved man after Isco's late header handed his side a 2-1 win over Real Betis, but he warned his side have a lot of improving to do.
Real looked set to drop two vital points in the Italian's first game in charge as they struggled to break through in the second-half after Karim Benzema and Jorge Molina had exchanged first-half strikes.
However, despite claiming the three points thanks to Isco's intervention four minutes from time, Ancelotti wasn't happy with how easily Real were opened up by Pepe Mel's side.
"I think we can improve, which is normal. We had many chances to score and a lot of good combinations, especially on the wing," said Ancelotti who has taken over from Jose Mourinho.
"The problem was in defence. In the first-half we didn't work well together and we had a lot of problems.
"It was a problem of balance. There was a lot of space between our defence and midfield and Betis played very well in this area.
"If we want to play quality football, we need players like Isco and (Mesut) Ozil to do defensive work. Right now it is a normal problem, but they are generous players and we need to find the balance."
On a typically hot August evening in the Spanish capital both sides seemed to tire quickly as the second-half wore on and Ancelotti believes the number of his players involved in international matches in midweek meant they struggled physically more than their opponents.
"Nine players who played tonight were not here this week as they were playing with their national sides and we didn't have time to prepare. Physically, Betis were better."
The former AC Milan, Chelsea and Paris Saint-Germain boss also made a big call in his first competitive game in charge by starting Diego Lopez in goal over club captain Iker Casillas.
Mourinho had also dropped Casillas in favour of Lopez for the last few months of last season, however Ancelotti refused to confirm that the former Villarreal keeper would be his number one this season.
"I took this decision for the match today. It was decision made on fine details and we will see what happens in the next match.
"I spoke with Iker, he is very professional and wanted to play which is normal and good."