Lou Piniella had indicated he wanted Marshall for the spot, created by Scott Eyre's elbow injury. Eyre did play catch on Thursday, but is expected to be placed on the disabled list at the start of the season.
However, Piniella switched on Thursday, and said Pignatiello was making a strong case for himself.
"The way Pignatiello is pitching, it's starting to make you review your choice a little bit," Piniella said. "Not that we don't like Marshall -- we do like Marshall. This young man [Pignatiello] has really pitched well this spring and he's pitching with confidence and he's done that role before."
In 10 innings over 10 games, Pignatiello has given up one run on five hits and no walks, and the one run was because of a dropped ball. He's been throwing an effective sinker and curveball, and has been tested in late-inning situations.
"He's made us re-think," Piniella said. "We're going to take this decision to Vegas."
Marshall has been used as a starter, and Piniella acknowledged the Cubs probably should have used the lefty in relief roles earlier this spring.
"We didn't think we'd have room on the roster for two lefties," Piniella said. "If we had done this a couple weeks ago, we'd have a clear-cut answer."
Eyre said he was still experiencing some pain in his elbow after playing catch Thursday.
"It's not free and clear yet," Eyre said. "But I'm not worried about it."
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.