Thome has been on the disabled list since Tuesday. He received an epidural on Thursday and was told at that time to rest for 30 days before resuming baseball activities.
He has no target date for his return, but mid-September would appear to be realistic.
Thome concedes that "the timing is bad."
If the Orioles are out of contention by that time, the 41-year-old slugger may not be needed.
Thome had two homers, six RBIs and 10 walks in 18 games since being acquired from Philadelphia on July 1. Since joining Baltimore, he has hit career homers No. 610 and 611 to pass Sammy Sosa for seventh on the career list.