Piatti will miss 8-12 weeks after stretching out the outer ligament on his right knee, an injury different from the ailment that kept him out two months earlier in the season. The Argentine suffered the injury against LAFC last Friday, which was just his first start back.
The 34-year-old had gotten off to another strong start this season before the injuries, with three goals over his first three matches. Montreal have gotten on well in his absence, currently sitting third in the Eastern Conference.
Piatti will have to wait to add to his MLS regular season totals of 66 goals and 34 assists.