Former Newcastle United and Fulham forward Aleksandar Mitrovic missed training with Al-Hilal because of an abnormal heart rhythm.
Local media has reported that the 30-year-old was taken to hospital after scoring for the Saudi Pro League champions in a 2-0 win at Al-Fayha on 7 March.
Mitrovic had just returned from a hamstring injury that had kept him out of action since January.
"The medical staff has decided to rest Aleksandar Mitrovic from Sunday's training, due to feeling fatigue and arrhythmias," Al-Hilal said in a statement., external
"He will be observed by specialists, as his case will be monitored constantly.