Koss (hamstring) had his rehab assignment transferred to Triple-A Sacramento on Saturday, and he went 1-for-5 with an RBI double in the team's 5-4 win over Las Vegas.
Koss began his rehab stint in the rookie-level Arizona Complex League on Thursday but was quickly moved to Triple-A. The 27-year-old reserve infielder was placed on the 10-day injured list July 1 due to a left hamstring strain, but his quick advancement to Sacramento bodes well for his chances of being activated soon.