Pato broke down in Milan's recent 1-1 draw with Udinese, and will be out of action for at least four weeks.
However, Allegri has graver concerns over the Brazil international's long-term health, suggesting the injury he suffered is not normal for someone his age.
"When these mishaps repeat themselves, it is unlikely down to just one single cause," Allegri said in his pre-match press conference.
"We have examined alongside the medical staff and it is not normal for a kid of his age to suffer this type of muscle strain.
"It is difficult to ascertain the cause of any injury let alone with Pato who has suffered eight, all at San Siro. but the ground is not to blame."
Pato has long been regarded as a potential world-class player, and has shown glimpses of his quality in the past.
However, his injury-proneness is threatening to hamper what was once predicted to be a glittering career.
Shifting his focus to the team, Allegri made it clear that Milan would go all out for a win in their next Serie A match against Cesena on Saturday.
Nonetheless, he did maintain that the Rossoneri's title hopes would still be very much alive een if they fail to get a result against Cesena.
"A victory now would be important, and it's essential in order to have the same number of points as we did at the same stage last season.
"But the championship is long, it does not end tomorrow [Saturday]."
Milan are currently 16th in the Serie A standings, after picking up just two points from their opening three league matches.