The Mexican star suffered the calf strain during training last week ahead of Saturday's El Trafico. After LAFC's 6-2 win over their rivals, Galaxy coach Guillermo Barros Schelotto said that Hernandez could miss up to four weeks, essentially ruling him out of the tournament, which concludes with the final on August 11.
"He had a knock in training, an injury that will take three weeks to recover, or four weeks depending on the seriousness and his recuperation," Barros Schelotto told reporters on a conference call.
Hernandez played in just one game for the Galaxy in Orlando, grabbing his first MLS goal, but also seeing his penalty saved, in a 2-1 defeat to the Portland Timbers.
Without their star man, the Galaxy will be looking for a much-needed victory when they take on Houston Dynamo in their final match of Group F on Thursday (8 pm ET | FS1, TUDN in US; TSN, TVAS in Canada).