Ferrara recalled Alessandro del Piero for the 3-0 win and was rewarded by a double from the captain.
"I had to tell him off, as he needs to let me be more relaxed on the bench!" laughed Ferrara. "He had the chances to finish off the game and should've taken them. He scored a good third, but he needs to help us all take it a bit easier.
"I wasn't here in previous games, so I don't know what happened and what was asked of the players. I know that I did request lots of hard work from Del Piero both in attack and coming back to help the defence."
It was Juventus' first win since March after a seven-match winless streak and marked a big turnaround from recent performances.
"Siena had a very strong start and created a few problems for us, but for the rest of the time I think Juve played with a real spirit of sacrifice from all its men.
"I believe that when there is a change of management, there is always going to be a shake-up in terms of motivation.
"Even if it wasn't me on the bench, the players would've felt responsible and realised exactly what it is we're gambling with here.
"We had to go and get the direct Champions League qualification and perhaps something a little more."