It was thought that Wood would be available for the weekend series against the St. Louis Cardinals.
"I think it'll probably be quicker than that, but we'll see," Piniella said.
Wood did try to lobby to get reinstated Monday night for the first of three games against the Houston Astros.
"I tried and it didn't work too well," Wood said of his efforts to convince Piniella. "Hopefully, in the next few days."
Carlos Marmol, Bob Howry or rookie Jeff Samardzija will take over the closer duties until Wood had pitched in at least one tuneup game.
"He's the manager," Wood said. "I'm going to do what he says. I just want to get back out there and pitch."
Wood and the Cubs' medical staff have tried every salve and remedy possible, some conventional and some not, to heal the blister on his right index finger. Anyone who doubts something so small could sideline him for so long has never been a pitcher.
"The chances are the people who are saying that have never picked up a baseball or thrown one," Wood said. "I can't worry about what people say. People in the game have had it before, know what I'm doing. That's all that matters to me. I'm looking forward to getting back out there."
The time off should benefit Wood, who has 24 saves in 29 opportunities. He originally thought he'd be back after the All-Star break.
"I got a little longer break -- I didn't want one, but I did get one," he said. "I should be strong for the stretch.
"It's frustrating when it's something as small as this," Wood added. "Any time you miss games and you're not part of the action and you're in a pennant race, it's no fun to sit and watch. I guess it made it a little easier because of the way we were playing."
What actually healed the blister?
"I can't tell you," Wood said with a smile.