The 22-year-old American suffered an ACL injury and will likely miss the bulk of the current season. "It's not a matter of weeks, we lost him for a long time," manager Peter Bosz announced during a press conference on Friday.
"When the severity of Pepi's injury became known, we immediately put our heads together," Bosz continued.
"We are still active on three fronts. Can we do that with only Luuk de Jong as a striker? That will be very difficult, so we are looking. Whether that will be something, I don't know.
Pepi has been PSV's top goalscorer so far with 17 goals in 28 appearances, of which just eight were starts.
Noa Lang
The league leaders will likely not lose Noa Lang, however. The talented winger has been heavily linked with a move to Serie A leaders Napoli, but Bosz does not want to lose Lang in January.
"That was known, right? That it was a ‘no’ for me?," Bosz asked. "It's not up to me, so I can't say anything else about it.
"If it's up to me, he will stay."
PSV continue their Eredivisie season this Sunday with an away game at NEC Nijmegen. The Eindhoven team are four points ahead of Ajax, who have played one less game.