Koch (2-2) allowed eight runs and nine hits in 4 1/3 innings, his poorest outing since moving into the rotation after Taijuan Walker underwent Tommy John surgery.
Milwaukee starter Jhoulys Chacin gave up one run on two hits in seven innings, with seven strikeouts and two walks. In four of those six games, the D-backs have scored less than three runs. Arizona has lost six straight games, and after holding the best record in the NL, they enter Tuesday's action with only a 1.5-game lead over the Colorado Rockies in the NL West. Tyler Saladino added a two-run, inside-the-park homer in the ninth for Milwaukee, which improved to 4-1 on its current 10-game road trip.
Daniel Descalso singled home Jarrod Dyson with two outs in the eighth to deliver the Diamondbacks, snapping a six-game losing streak. Chris Owings was walked intentionally to get to the left-handed Descalso, who singled through the defensive shift in right field to put Arizona ahead.
Archie Bradley (1-1) struck out two in a ideal eighth to get the victory.
Name change is expected to be adopted 15 May 2018
The company has established a presence, meanwhile, outside of the conventional energy sector. On Wednesday morning, Norwegian oil major Statoil will formally remove "oil" from its name.
Steven Souza Jr. doubled in his first run as a D'back in the fourth. This will be Koch's first career start against Milwaukee.
No player has been as important to the Diamondbacks this season as center fielder A.J. Pollock.
"I don't even want to get there until we know what's going on tomorrow" manager Torey Lovullo said after last night's game.
The Diamondbacks didn't get a hit off Guerra until Paul Goldschmidt's double in the fourth, when Arizona scored twice to tie it at 2. It was good for the final two runs of a three-run insurance rally, which was critical since it meant closer Corey Knebel could rest in the bottom of the ninth in favor of another Brewers reliever, Williams.