Cortes was scheduled to make a third minor league rehab start Wednesday. When he arrived to get his things and travel to Triple-A Scranton/Wilkes-Barre, the left-hander was told he would start this weekend.
"I was made aware of it today before I got in. I was supposed to come and pick up my stuff before I got to Scranton," Cortes said before the Yankees concluded a three-game series with Tampa Bay. "That's kind of what I know."
Cortes is starting in the spot where Domingo Germán would have possibly started. The Yankees announced Wednesday Germán has voluntarily entered inpatient treatment for alcohol abuse.
Cortes will throw one more bullpen session Thursday and likely be limited to around 60 pitches in his first outing since May 30 in Seattle when his shoulder started bothering him.
Cortes was initially placed on the 15-day injured list June 8 and hoped to only miss two or three starts. The Yankees moved him to the 60-day injured list July 7.
"I've been on the shelf too long," Cortes said. "I want to come back and obviously show who I am and be back to the same form I was. So excited for this weekend."
Cortes is 5-2 with a 5.16 ERA in 11 starts and has particularly struggled later in outings. Opponents are hitting .447 when facing him for the third time in a game.
Last year, Cortes was an All-Star and went 12-4 with a 2.44 ERA in 28 starts.
Yankees manager Aaron Boone also said Luis Severino will make his next scheduled start Friday against Houston. Severino allowed nine runs and 10 hits in 3 1/3 innings in a 9-3 loss at Baltimore on Sunday.
He is 2-5 with a 7.49 ERA in 12 starts this season.
Severino threw a bullpen under the guidance of longtime Yankees starter and new pitching advisor Andy Pettitte and said it went well.