The veteran Italian will have scans tomorrow to assess the damage after an already disappointing performance was compounded when he trudged off injured in the first half of the Sky Blues' 2-0 win over Newcastle on Saturday night.
Del Piero is almost certainly going to miss this weekend's trip to Gosford to face defending champions Central Coast Mariners and if the scans indicate any type of tear, the 39-year-old is likely to miss much of the hectic festive schedule.
"I had a chat to him and he's quietly confident everything is going to be okay," Sydney FC midfielder Matt Thompson revealed today. "But I don't want to jump to conclusions.
"We can work well as a team whether he's out there or not. We've got a strong 23 players in our squad and we showed that on the weekend."
Normally heading into a game without their marquee man would spell trouble for the Sky Blues but the club is riding high on the back of a club record four-game winning streak.
While they have lost every game this season that Del Piero hasn't started, Thompson said there was a newfound belief in the squad.
Much of that confidence comes from the side's ability over the last month to eke out results despite a host of injuries and suspensions making it difficult for coach Frank Farina to name a settled squad.
Rhyan Grant (knee), Peter Triantis (groin) and Terry Antonis (thigh) are sidelined indefinitely through injury, Brett Emerton (calf) is no certainty to return while defender Tiago Calvano is serving an eight-game ban.
And Thompson believes Sydney's ability to get results despite the personnel upheaval will help the squad come the business end of the season.
"It's important for us that we have that self belief that no matter who's out there we can do a job," the former Jets and Heart midfielder said.
"The fact that we've used so many players, it would be hard for teams to prepare for how we'll play so that can really be an advantage for us.
"Joel (Chianese) has stepped up this year, Ali (Abbas) is playing left back and Mat Jurman came in in defence on the weekend and it's like he's been playing there for 10 weeks.
"I think a few people may have thought with Alessandro coming off it might have been a blessing for them but for us it may have been an advantage."
Asked the reasons behind the Sky Blues' record-breaking run, Thompson said: "The last couple of weeks we've had a game plan and stuck to it.
"The big word there is consistency and the teams that do that in the A-League find themselves in the top two or three at the end of the season and that's definitely the plan for us.
"It's important that we put ourselves in a position where if there's any slip ups throughout the season you're not dropping back outside the top six."