Gennett has been struggling early this season for the Brewers, batting .154 with a .203 on base percentage, with one home run and three RBIs. The 25-year-old has been Milwaukee's starting second baseman since July 2013. He batted .324 in 69 games as a rookie in 2013 and .289 in 137 games last season.
Gennett also spent time on the 15-day disabled list his year after he cut his hand on a piece of metal while showering.
Knebel is 1-2 this year with Colorado Springs with a 4.70 ERA and six saves.
Entering Monday, the Brewers are 13-25 and are 12.5 games behind the St. Louis Cardinals in the NL Central.
- Jack Jorgensen