The Cubs decided to have Prior throw after he felt no discomfort from his throwing session on Tuesday.
"There's never been a timetable because nobody really knows a timetable," Prior said. "We're evaluating the day after workouts to see where we're at and where I'm at, obviously, and then have discussions as to what our next step would be. That's what we did Wednesday, and we made the determination that if we could use the field today, we'd try to throw to some hitters and get a workout that way.
"For the most part, I thought I threw well," Prior said.
Baker also refused to put a timetable on when Prior could come back.
"I'm holding that in reserve," Baker said. "We're happy to get him on the mound, period."
Macias thinks Prior is ready.
"He was sharp, he's got good stuff," said Macias, who did hit a home run off Prior. "I didn't think the fastball would be that hard, but it jumped. And the off-speed, the curveball, wow. It was good. He'll be back soon."
Prior said he'll know more on Saturday after he sees how his right elbow responds to the work.
"I don't know what the so-called schedule is going to be," he said. "My arm feels good and it felt like my strength was there. Obviously, my endurance isn't there. I felt a little tired at the end. Overall, it was a good session and a good workout."
This was Prior's first visit to Yankee Stadium. Maybe it's fitting he threw here. Prior was drafted by the Yankees in 1998 in the supplemental round between the first and second rounds of the June draft. Obviously, he did not sign with New York.
"I checked it out," he said. "There are pretty cool monuments and stuff out there. When you first walk out, it's like what you see on TV. But when you get on the mound, it's just a mound and just a plate. Especially when there are no fans -- it's like being almost at HoHoKam [Park in Mesa, Ariz.]. I'm sure when the fans fill up, you'll get more of a sense as to what it's like to play here."