Andrea Pirlo described Federico Chiesa as "naive" after he was sent off on his debut in Saturday's 1-1 Serie A draw against Crotone.
Chiesa, who joined the champions on loan from Fiorentina on transfer deadline day, saw red on the hour mark for a late challenge on Luca Cigarini.
He had earlier set up Alvaro Morata for Juve's leveller after Simy had given Crotone the lead from the penalty spot.
Adrien Rabiot was dismissed in the 2-2 draw with Roma on September 27, Juve's last competitive game after they were handed a 3-0 win for Napoli's no-show last time out, and Pirlo accepts his fledgling side's over-enthusiasm might come back to haunt them on occasion.
"Unfortunately, we went down to 10 men in the last two games because of our errors, but we are a young team that needs to work and there hasn't been much time for that with so many internationals," he told DAZN.
"Young players need to gain experience by playing in matches and it can happen that they make naive errors as part of the learning process.
"We built a team with quality, but it is still a work in progress and needs time. The lads will learn through mistakes, unfortunately that also means taking a few risks in the early matches of the season.
"We made a few mistakes in the timing of the press, but as I said, these things happen when we're still getting the machine oiled. We only really spent half-an-hour on this tactical movement in training yesterday, so it will improve."
Crotone were good value for their first point since returning to Serie A, limiting Juve to just two shots on target, and their boss Giovanni Stroppa says his side can take pride in their performance.
"Serie A is another sport compared to Serie B," he said. "We've conceded a few goals with naive errors, but I still believe we are on the right track.
"We could've made more of the extra man and been sharper in the final third, taking them on one-on-one, but we still did well with 11 against 11 and 11 against 10.
"This is not the best Juve team, but we saw they still had remarkable talents to come off the bench and bring new elements to the side, so we can be proud of this result."