Knebel is in his second stint with the Brewers this season. He appeared in five games last month, going 0-1 with an 8.31 ERA before being sent down. The right-hander opened the season on the disabled with a strained left oblique.
In 11 games at Triple-A, Knebel was 1-0 with a 1.32 ERA, allowing only five hits in 13 2/3 innings.
Knebel took the roster spot of right-hander Michael Blazek, who was optioned to Colorado Springs last Sunday.