Del Piero was injured when Sydney FC fell to the worst defeat in the club's history last week when they were handed a humiliating 7-2 loss against Central Coast Mariners,
The former Juve star urged his team mates to put the result behind them and focus on the upcoming match against Melbourne Victory.
"We talked a lot, I don't think too much, but a lot about last Saturday," Del Piero said. "It's a really bad loss for us. We are really disappointed about what's happened. But Saturday we have another match.
"If we think too much about last Saturday, maybe we go on the field with some fear or something and it's not positive."
When asked on what the team could improve on from the last match, Del Piero said: "What? Maybe everything if we saw the last match. No, we did some good things ... but in the end the game last Saturday for us was a very, very bad day.
"That's why I try to joke because if we think about it too much maybe there will be much pressure on us. We understand it's not a good day for us but we have another game on Saturday."
Sydney are also missing former Australia international Jason Culina through injury, who is expected to be back later in the month.