The Brazil international joined Juve in the summer from Aston Villa, but has struggled to make an impact in Serie A due to form and fitness.
Responding to Luiz's latest round of snaps on Instagram, one Juve fan posted, asking if he had joined the club only to take pictures.
In response, Luiz ranted: “I didn’t come here just to take pictures; nobody else did. I want things to be different. I came with a purpose, I listened to my heart when I signed. Now, I want you to answer me: why hasn’t a signing like me played two consecutive matches with this shirt?
“You can say whatever you want to the press later: ‘Douglas isn’t fit.’ Am I not fit? I did the entire pre-season and played every match.
“I had come off one of the best seasons of my career, one of the best defensive midfielders in the Premier League. Injuries held me back. True.
“But how long did I stay on the bench while I was fit? A lot. These injuries were not normal. I’ve never been injury-prone, but there are many reasons that could have caused this, which I’d rather not comment on. I will keep giving everything for this club, even though it’s hard sometimes. It’s not easy, but you can count on me.”