PSV will be without midfielder Andres Guardado for at least a month after he damaged ligaments in his ankle against Manchester United.
The Mexico international suffered the injury 20 minutes from the end of the 2-1 Champions League Group B victory on September 15, and was subsequently replaced by Stijn Schaars.
Guardado was not present for Saturday's surprise Eredivisie defeat at the hands of Heracles, and scans have revealed the extent of the problem.
"Andres Guardado will be sidelined for four to six weeks after sustaining an ankle injury," PSV announced on Monday.
"Guardado underwent an MRI scan in hospital on Monday afternoon.
"Last week, the ankle was still too swollen but a second scan has determined the Mexican will be out of action for four to six weeks."
Guardado had been a regular in Phillip Cocu's side this season after making his loan move from Valencia permanent at the end of the previous campaign.
