Antonio Conte rang the changes and then hailed Chelsea’s new Costa after the Blues’ ruthless return to the Champions League.
New £23million full-back Davide Zappacosta had Stamford Bridge in awe after his fluke cross-shot helped to crush Qarabag.
Pedro, Cesar Azpilicueta and Tiemoue Bakayoko all weighed in while Michy Batshuayi and an own goal completed the rout to match the club’s biggest ever win in the competition – with star striker Diego Costa still in exile.
Conte said: “First game in the Champions League, I decided to start with a rotation. We have to start a process to improve our players.
“Davide has said he wanted to cross, but he scored and it was an important goal for us.
“I’m really pleased with his performance. Now we have to continue to play with him and the other players. Tonight I had a positive answer from my players.”
“He played a really good game. Now he has to continue to work to improve, but for sure, Davide knew very well my style and idea of football. For this reason I decided to start with him. He was prepared to play, and played very well.
“It’s not easy to change your sporting life totally in only one week, but the answer was really good.”
Chelsea last scored six in the Champions League against Maribor in 2014. Conte made four changes from the side that beat Leicester last weekend. His B team responded with the club’s fourth consecutive win.
Conte said: “I think it was a perfect start for us to play our first game in the Champions League and win with a good result. To score many goals. To finish the game with a clean sheet. I saw a lot of positive things tonight.
“Now we have rest tomorrow and then to start to think about the next game, a tough game against Arsenal.
“To play in Champions League, it means the coach trusts you. My message tonight was this: I trust all my players, not only with words but with actions.
“We would be crazy to think we could play with only 13 players like last season. So we have to improve all these players to try and create a positive competition between them. This is very important.
“Our way, our style of football, is always to try to push from the start until the end.”
Cesc Fabregas admitted afterwards that he is dreaming of adding the Champions League to his glittering array of trophies having lifted the World Cup and Euros with Spain and Premier League with Chelsea.
He said: “We have waited a long time to play in the Champions League.
“Finally it has arrived and it is a good performance. A good result. And you never know if the goals will count at end of the group stage. We just keep going now.
“We focus on Arsenal, a tough game on Sunday, a very difficult period for us. We have to be on top form. The coach always says, ‘eat well, sleep well’, and we have to recover well for Sunday.”