Chandler, the No. 1 pitching prospect in all of baseball, gave up just two hits while striking out three and walking none in his debut en route to a 9-0 win.
Starting pitcher Braxton Aschraft, also a rookie, earned his fourth win of the year, bringing his earned run average down to 2.70.
The 22-year-old not only recorded a four-inning save, but he is the very first pitcher in Pirates history to ever record a save in his debut.
Pittsburgh dealt closer David Bednar to the New York Yankees at the trade deadline this season, leaving the spot open for whoever steps up.
Chandler had a 4.05 earned run average through 26 starts in Triple-A this year, giving up 95 hits and 53 walks through 100 innings while striking out 121.
Opposing bats were hitting .250 off Chandler in Triple-A, leaving him with a less-than-favourable 1.48 WHIP.
Chandler originally thrived in Triple-A when he was promoted last season, posting a 1.83 ERA in seven starts, striking out 54 in 39.1 innings with opposing bats hitting just .183.
Pittsburgh selected Chandler with the 72nd overall pick (third round) of the 2021 MLB Draft out of North Oconee High School in Bogart, Georgia.
Pittsburgh recently called up MLB's No. 1 prospect Konnor Griffin to Double-A (read more here).