"Most of this was brought about within a day or two after he came out of the game initially," O'Neal said. "Things had been improving, but we requested he go ahead and go through with this opinion."
Zambrano has only thrown on flat ground so far, and said he might throw a bullpen session on Monday.
"He hasn't gone backward at all," O'Neal said. "This was set up five, six days ago. Sometimes you hear from other people and it'll be reassuring."
O'Neal said after Monday's game that Zambrano will be examined on Wednesday by the Cubs' team doctor to gauge whether the pitcher is ready to do more than play catch.
The Cubs have yet to name a starter for Thursday, which would be Zambrano's spot in the rotation. Wade Miller, who filled in Saturday and went three innings, is a candidate.
"It could be [Miller]," Cubs manager Dusty Baker said. "We have to see how he feels after the other day. We'll see."
Welcome back: Shortstop Cesar Izturis was in the starting lineup on Monday, his first game since Aug. 21. He had been on the disabled list with a strained right hamstring.
"He's been working real hard to get back," Baker said. "He's champing at the bit and ready to play."
Izturis has been taking batting practice and is able to take ground balls and run without a problem. However, he won't be playing every day, but eased back into action. He'll skip Tuesday's game, for example, then play two, then likely get a day off.
"He won't play Tuesday. His leg could be tired, sore," Baker said. "He'll be off, then play couple days in a row, then off a day. We'll see after that."
Izturis said he didn't want the injury to carry over into the off-season.
"I want to make sure it's better," he said. "My goal is to go out there and try to get on base and try to score some runs."
On Monday, Izturis batted seventh, but Baker projects the shortstop as a No. 2 hitter.
Hit machine: Juan Pierre entered Monday's game second to Colorado's Matt Holliday in the National League in hits. Holliday has 179, Pierre 178. If he stays strong, Pierre could take over the lead. He was the top hitter in 2004 with 221 hits.
"He's done it before," Baker said. "I always say water seeks its own level, and you're going to be pretty close to where you are, career-wise. That doesn't surprise me at all, really. If anybody's going to do it, it's Juan. He's a guy who, when he gets hot, he gets super hot and can get a whole bunch of hits in a short period of time. Usually guys who lead the league in hits don't walk a bunch."
Pierre doesn't walk much. He's walked 32 times this season.
"He's tried," Baker said.
Memories: Monday marked the five-year anniversary of the Sept. 11 terrorist attacks, and Baker recalled being with the San Francisco Giants in Houston. They were about to begin a series against the Astros.
"I got a call from [coach] Sonny Jackson," Baker said, recalling what happened the morning of Sept. 11, 2001. "He said, 'Man, you better turn on the TV.' He said, 'That's all I can tell you, please turn on the TV.' I turned it on in time to see the second plane.
"I thought that was the first plane, like a replay," Baker said. "That was one of the most horrible things I've ever seen."
He called a friend in New York to make sure he was OK, but found out that person's fiance was in one of the Twin Towers.
"Then you just sat there for a long time in shock," Baker said.
He didn't watch the newscasts on Monday.
"I knew it was on there," Baker said. "It's tragic. You felt good about how America responded and rallied around everybody in New York, and the bravery of the policemen and firemen there. It made everybody come together."
The 2001 season was special for Cubs television announcer Bob Brenly, who was the manager of the Arizona Diamondbacks that season. They had to face the New York Yankees in the World Series, and won in seven games.
"It was a very touchy situation from a [public relations] standpoint," Brenly said Monday. "Obviously, New York had suffered tremendously. I think Scott Brosius said it, if there was any right time for the Yankees to win it, it was that year. That wasn't our viewpoint. We felt deeply for what happened and had sympathy for the people who suffered, but we had a job to do."
"We had to tread very lightly and be careful about the things we said," Brenly said. "How can you prepare for that? How do you know how to act? I was very proud of my guys."
Brenly and some of the Diamondbacks players visited Ground Zero when they were in New York for the series. Several players chose not to go.
"For the guys who did go, it was a very humbling and gratifying experience," Brenly said. "To see these guys who were real heroes looking up to Randy [Johnson] and Curt [Schilling] -- they were handing cell phones to these guys to talk to their kids at home."
"It was something I wish I didn't have to experience," he said, "but given the circumstances, I'm glad we went through it."
Sing along: The identity of Tuesday's seventh-inning stretch singer is to be determined. On Wednesday, former Cub Doug Glanville will sing "Take Me Out to the Ballgame," followed on Thursday by former Dodgers manager Tommy Lasorda. Friday is also TBD. On Saturday, John Weiderman, the play-by-play announcer of the Chicago Blackhawks, will sing, and Ron Santo will lead the crowd on Sunday.
Good cause: The Cubs wives and Bank of America will host the fourth annual food drive on Saturday at Wrigley Field. Donations will be accepted from 1 p.m. CT until the third inning at the corner of Sheffield Avenue and Addison Street.
Minor matters: Boise scored four runs in the top of the eighth but lost, 6-4, to Salem-Keizer, which won the Northwest League Championship, three games to one. Jacob Renshaw gave up four runs -- three earned -- on five hits over three innings and took the loss. Tyler Colvin batted 7-for-17 in the playoffs. Russ Canzler had two RBIs and two hits.
On deck: Lefty Sean Marshall will open the Cubs' three-game series against the Los Angeles Dodgers on Tuesday night at 7:05 CT. The game will be broadcast on WGN Radio and Comcast Sports Net.