"The ball actually got thrown into the stands. I won't say who threw it," Wood said. "It's just a ball. I can grab any dirty ball and write on it."
Cubs manager Joe Maddon didn't specify what relief role Wood will have. The Cubs announced after their 3-0 loss to the Pirates on Sunday that left-handed starter Tsuyoshi Wada will join the rotation from Triple-A Iowa and will start Wednesday against the Padres. Wada, whose rehab assignment expired, has been on the disabled list since March 27 for a mild left groin strain.
As for Wood, Maddon said he's comfortable with him in various situations. He has a 0.00 ERA in five career relief appearances.
"It depends on who's available that night," Maddon said about Wood's role. "We've got some really good left-handed pitching out of the bullpen. It's just going to be based on leverage and situation. I'm not afraid of him anywhere. Woody, having been a starter, knows how to get out good right-handed hitters, too."
Closer Hector Rondon had pitched on three consecutive days, so Maddon wanted to avoid using him against three batters on Saturday. So the Cubs turned to Wood, who would have departed after facing a third batter, Maddon said. Wood got two flyouts and a popout on 10 pitches, so another reliever wasn't needed.
Maddon noted that Wood could return to starting eventually.
"I have a lot of faith in this guy coming out of the 'pen," Maddon said. "[I told him to] just go out there and be aggressive, assertive and let it go for an inning or two. I think when he does that, he can be really good. I'm eager to see that. We also talked that this does not preclude the potential for him to become a starter again at some point."
Wood (2-2, 5.45 ERA) has allowed 17 runs (15 earned) in 13 1/3 innings in his past three starts.
"I'm going to do everything I can to pitch the best I can out of there," Wood said. "It's going to be no different pitching-wise. Maybe it allows me to iron some things out and throw good ball."
Wood conceded he will likely get fewer at-bats now that he's in the bullpen. He's hitting .184 with nine home runs in his career.
"My at-bats haven't been what they used to be, so maybe we needed a little break from that as well," Wood said with a smile. "Hopefully we'll get that ironed out as well."
Wood said he was unsure of his exact role and how long this assignment will last, but he can throw on back-to-back days.
"On a personal level maybe a little bit [it's disappointing], but as long as I'm here and can help the team win -- we're playing great baseball right now," Wood said.