El Bilal Toure scored Stuttgart's winner, with Danilo being sent off for Juve and Perin also saving a penalty for the hosts.
“Stuttgart certainly deserved it, they were better than us from the first minute. We must digest this defeat as quickly as possible, maybe a night and a day, then get back on our feet to prepare for Inter,” Motta told Sky Italia.
“We were unable to remove the control of the game that they had. In the first half, they would beat the press with the right-sided centre-back and when you do not control the game, you will struggle. Stuttgart are a tough team to face and they deserved to win.
“We suffered their tempo today certainly and most of the time they had the initiative. We struggled to impose our style on the game. There are many things to analyse about Italian and international football, there are teams who want to keep the ball, press high and that gives you very little time to rest. This is the level.
On his squad options, Motta insisted: “Building the squad was shared with the club. I agree we need to do more in attack to compete with a team like Stuttgart, but in order to play well, we need to be much better in defending than tonight.
“We allowed Stuttgart to control the game and when we got the ball back, we struggled to build anything and were not in a condition to do well.
“A team has to defend well so it can recover the ball and then use it well. We suffered out of possession, while the most we managed in attack were a few counters. I take responsibility for that, we must improve for the next games and that starts against Inter.
“We will try to improve what we can improve and keep working.”