Just so we are on the same page, which one was the good one? The one that he gave up two runs in six innings against Milwaukee, the one where he gave up two earned in six innings against the A's, or the one where he pitched six scoreless innings against the Giants? Because I'm assuming you aren't counting the last game he pitched before this weekend, where he retired all three batters he faced.
He's 23 years old. Have some patience. As a 23 year old Mitch Keller had a 7.13 era in the majors, including games with five runs in five innings, eight runs in four innings, six runs in 4-1/3 innings, six runs in three innings, and six runs in four innings. Good thing they didn't give up on him then, huh?