Manager Dale Sveum put his erratic shortstop on notice by calling it "the last straw,'' but that wasn't the lecture Castro dreaded most. Disappointing his manager was one thing. Letting down his mentor, Alfonso Soriano, was another.
Castro lived with Soriano, 36, parts of the previous two seasons but became especially close during spring training as a Chicago police investigation loomed over the Cubs' best player. It was the counsel of Soriano that Castro, 14 years younger, credits with keeping him focused until local prosecutors decided against filing charges.
"He was always telling me it would be OK, talking to me how to mature,'' Castro said. "I want to be like that one day.''
These days the young Cubs believe "Sori" has as many answers as Siri. Even Soriano shook his head at a career evolution from flamboyant slugger to quiet clubhouse leader.
"I never thought at a young age that I would be a role model for my teammates,'' Soriano said.
Good luck finding one of those teammates to offer anything but praise for Soriano, perhaps Chicago's most misunderstood athlete. Nothing confirmed that more than the overreaction Saturday night at Wrigley Field to Soriano not running out a line drive that popped out of the glove of Red Sox third baseman Will Middlebrooks.
"There's not a guy in the history of baseball who doesn't react the same way on that play,'' Sveum reiterated Tuesday.
Cubs fans unleashed a pent-up chorus of boos anyway. They booed because Soriano has been caught loafing before and because he occasionally poses after home runs. They booed because Soriano still has two years left on an eight-year, $136 million contract and he represents life before the Theo Epstein era.
They booed a proud veteran whose workmanlike manner makes him the type of player Chicago typically embraces. At this stage of his career, Soriano offers more grit than flash, and in a Cubs season in which forming habits means more than winning games, his approach to the job has a bigger impact on the organization than his approach at the plate.
On an impressionable team, that kind of attitude potentially goes even further than any of Soriano's homers — as was evident in the way Cubs players defended their teammate. Reed Johnson blogged — more like bragged — about Soriano. Matt Garza called criticism of Soriano "freaking ridiculous.'' Tony Campana offered similar praise. It might be easier to list Cubs who didn't look for a microphone.
"They know how hard I work,'' Soriano said. "That's what I do to be a better player and teammate and show the young guys that's the only way you can get better. They know who I am.''
He is the guy who showed up at 2:45 p.m. Tuesday at the Cell, before most teammates, because his ailing left knee and tight hamstring require extra time. After early stretching and flexibility exercises, Soriano usually takes extra outfield with fellow 30-something teammate Reed Johnson.
"You don't see too many guys 36 years old doing early fly balls to get better on defense,'' Johnson said. "People who are with him 24/7 know what kind of person he is.''
People who aren't make understandable assumptions. In the past two days, even Sveum and Epstein acknowledged this wasn't the Soriano they expected based on reputation.
"A huge surprise,'' Sveum said.
A bigger shocker would be the Cubs finding a taker for Soriano, who would accept a trade to a contending team that would be the best for everybody. He insisted he enjoys Cubs fans despite their latest outburst and dismissed a reporter's question if, in retrospect, he would sign with the team again.
"Yeah, why not?'' Soriano said. "I never had frustration. I love what I do.''
He would love it more if the Cubs were more committed to winning now than later. Most days that hurts Soriano more than his joints.
"It's very hard,'' Soriano said. "I'm not playing this game to lose. I'm a winner. Winning is fun. Losing is not fun. Losing makes me miserable.''
Not that the pro's pro lets it show through the pain.