"It's not what I expected, but it's kind of a good way to get the career started," Koch said. "It's been awesome, I'm honored to be here. It's awesome to be around a great group of guys, they've been awesome to me and very welcoming, so it's been a lot of fun so far."
Earlier this homestand, Koch made his Major League debut against the Giants. He pitched a scoreless 11th inning, despite issuing a pair of walks, in an extra-innings loss.
Koch allowed just two hits and a walk during his four-inning save Tuesday, striking out four.
"I've been throwing long innings all year, so it's something I'm used to," Koch said. "That's pretty much what I was ready to do when I got here. I'm just attacking guys, just try to trust your stuff and go with what you've got and see what happens."
Koch, Arizona's No. 19 prospect as ranked by MLBPipeline.com, pitched in Triple-A Reno and Double-A Mobile during his first season in the D-backs' organization. He was acquired on Aug. 30, 2015 in a deal that sent reliever Addison Reed to the Mets.
Between Reno and Mobile, Koch went 6-6 with a 4.08 ERA in 21 starts.
"He'll definitely get opportunities to start next spring, he'll compete," Arizona manager Chip Hale said. "I know [Reno manager] Phil Nevin has spoke very highly about him handling the [Pacific Coast League], which is not an easy league to pitch in."
Mitch Haniger was named Arizona's organizational Player of the Year, while Anthony Banda earned the Pitcher of the Year honor, the D-backs announced Wednesday.
Haniger, 25, hit .321 with 25 homers and 94 RBIs in 129 games between Mobile and Reno. He earned his first promotion to the D-backs on Aug. 16.
Banda, 23, went 10-6 with a 2.88 ERA in 26 starts between Mobile and Reno. He was named a Southern League All-Star and represented Arizona in the 2016 All-Star Futures Game at Petco Park during All-Star week.