Feyereisen (biceps) fired a perfect sixth inning in Triple-A Durham's win over Jacksonville on Wednesday.
The outing was Feyereisen's second rehab appearance, with his first having come with the FCL Rays on Monday. The 28-year-old threw 10 of his 13 pitches for strikes in Wednesday's appearance, but the the team's official site reports he's still estimated for a late-August return at the earliest.