Pelfrey, on the 15-day disabled list with a strained left groin since May 2, went five innings in his first rehab start, giving up one run on five hits and a walk against Triple-A Columbus.
He threw 81 pitches with 53 going for strikes, and is expected to need at least one or two more rehab starts before rejoining the Twins.
Willingham, who is on the 15-day disabled list retroactive to April 7 with a small fracture in his left wrist, started at designated hitter for Rochester and went 0-for-4 with a strikeout.
Willingham will need to play in several more games at Triple-A until he makes his return to the Twins, as he's been out for more than a month. The Twins want to see that he's healthy and productive before he makes his return.