Haeger, reunited with knuckleball mentor Charlie Hough, the 66ers' pitching coach, walked two, struck out two and was the losing pitcher.
Haeger was placed on the 15-day disabled list May 9 with what was announced as plantar fasciitis. Because he is out of options, he cannot be sent to the Minor Leagues without clearing waivers and the risk of being claimed by another team.
At the time he went on the disabled list, Haeger was 0-4 with an 8.59 ERA and had just been unable to retire any of five batters in a May 8 start against Colorado.
Meanwhile, disabled Opening Day starter Vicente Padilla continues to play a firm catch on flat ground with no further discomfort from the inflamed radial nerve that sent him to the sidelines, but he has yet to throw off a mound.
He will need several bullpen sessions and at least three Minor League rehab starts before he returns, which manager Joe Torre said remains some time in July.