The Cardinals spotted Aker an early lead and the rookie right-hander made it stand for a 8-0 victory over the Danville Braves on Sunday at Dan Daniel Memorial Park.
Aker worked 5 1/3 scoreless innings, holding Danville to three hits while striking out seven batters and walking two.
The Cards have won four of their last five games. Sunday’s game was their second shutout win of the season.
Kevin Woodall had a two-run home run in the third inning as Johnson City opened a 5-0 lead. It was Woodall’s eighth home run and his fifth in the last five games. Woodall added an RBI single in the fourth.
Luis Flores had three doubles in his 4-for-4 night for Johnson City.
Danville threatened Aker in the fifth inning, getting two runners on base with no outs, but he worked his way out of trouble without giving up a run.
Aker was an 18th-round draft pick out of the University of Tampa who began his college career at North Carolina. He was 3-0 in the Gulf Coast League before being called up Tuesday.
His promotion is expected to bolster a pitching staff that was next to last in the league with a team ERA of 6.44 going into Sunday’s game.
Junior Gonzalez relieved Aker in the sixth inning and worked three shutout innings before turning it over to Juan Alvarez to get the final two outs of the game.
Michael Perri’s RBI double in the second inning got things going for the Cardinals. Flores added a two-run double in the same inning. Perry went 3 for 4.
The Cards improved to 14-16, while Danville fell to 15-16. The two teams will square off again Monday with a 7 p.m. start.
Sunday’s Elizabethton Twins home game against the Princeton Rays was rained out. The teams will play a doubleheader at Joe O’Brien Field on Monday beginning at 5 p.m.