After a brief hiatus, the Inbox is back. Carlos Zambrano, Tyler Colvin and Starlin Castro are among the topics in this week's Cubs Inbox. E-mail your questions to cubsinbox@gmail.com, and please include your full name and hometown.

What are the Cubs thinking by sending Zambrano to the 'pen? Why not sign a free agent like Jason Isringhausen or Braden Looper. They could sign both if they wanted to. I don't see the logic in an $18 million setup man. Please, if there is any logic behind this move, could you inform the masses.
-- Kevin B., Beecher, Ill.

If you don't factor in Zambrano's salary and objectively compare him to the other Cubs starters, it makes sense. With Ted Lilly coming back, it looked like either Carlos Silva or Tom Gorzelanny was headed to the 'pen to make room. But Silva battled shoulder problems last year in Seattle. You need a durable setup pitcher. That's Zambrano. Gorzelanny never pitched in relief until last season and it didn't work well. He has to start. Ryan Dempster and Randy Wells have been terrific so far, and Lilly threw six shutout innings in his first start.

What the Cubs are thinking is they need help in the setup role, and if you take personalities and payroll out of the equation, Big Z makes the most sense. Plus, he was willing to do this. The momentum may have shifted in the National League Central on Saturday night when Zambrano began his new job as a setup pitcher.

"The bottom line is that at this particular time, it makes us a better club," general manager Jim Hendry said. "[Zambrano] didn't throw poorly. [Silva and Gorzelanny], their arsenal isn't conducive to going to the 'pen. ... There's no agenda at all, except it was the best fit at the time. He's capable of doing it."

Hendry looked for an experienced setup pitcher all offseason and couldn't find a good match. Isringhausen and Looper are both high risk because of their past injuries. If the Cubs made a mistake, it was counting on rookie Esmailin Caridad to be able to handle the setup role after his September outings. Caridad has the stuff, but he's a rookie, and when he returns, he can be eased into appearances in less pressure situations. Angel Guzman would have been great in the bullpen, but he couldn't be counted on for the setup role because of his past history of shoulder and elbow problems.

Zambrano has said he will do this until the Cubs find another setup pitcher. Nobody knows when that will be.

"I don't have a time frame," Hendry said. "It makes us a better club right now. All the other guys are pitching great. A month from now, somebody may slip up or someone has an injury and things change."

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Which means Zambrano could move back into the rotation. By that time, Caridad may be more effective. One thing is clear, salary was not a factor.

"You can't worry about anybody's individual salary," Hendry said. "Things change. People adjust. We're going to have an injury or two along the way, and we'll adjust to that. ... Nobody ever breaks camp with the 25 in the same role and just run the table, win 100 and goes to the playoffs. To get hung up on what somebody makes or what they used to do or what's going to happen a month from now or who you're going to acquire, that's foolish thinking."

I've been a Sean Marshall fan since he became a member of the Cubs. Checking the stats from the April 11 game vs. the Reds, I noticed that Marshall pitched two-thirds of an inning, resulting in one hit, but no earned runs (continuing his scoreless streak). However, he was credited with a blown save. Is this accurate? How can someone not allow any runs and get charged with a blown save?
-- Dan Y., Oklahoma City, Okla.

Marshall came into that game to relieve Gorzelanny with the Cubs ahead, 1-0, and the bases loaded. It was a save situation for the lefty, and he promptly allowed an RBI single to Miguel Cairo. Although the run isn't charged to Marshall, a blown save is charged to the pitcher who is on the mound when the tying run scores.

What is the average WHIP in the National League or Major Leagues? What is considered good (like a 3.00 ERA or a .300 batting average)?
-- Darrell C., Munster, Ind.

First, let's explain what WHIP is. It's a sabermetric measurement for the number of baserunners a pitcher has allowed per inning pitched. To determine it, you add walks plus hits and divide that by innings pitched. It's considered a more effective way to determine a pitcher's effectiveness.

A WHIP of 1.00 or smaller over the course of the season will rank among the league leaders. The lowest single-season WHIP was set by Pedro Martinez in 2000, when he gave up 128 hits and 32 walks over 217 innings for a 0.7373 WHIP. In 2009, Arizona's Dan Haren led the NL with a 1.00 WHIP, and Kansas City's Zack Greinke was tops in the American League with a 1.07 WHIP.

Through Monday, Silva was leading the Cubs and the NL with a 0.77 WHIP. But it's early. Ted Lilly is third among the Cubs and he's only had one start. What's encouraging is that Carlos Marmol has a 0.94 WHIP. Compare that with Jeff Samardzija, who gave up five hits and six walks over 3 1/3 innings for a 3.30 WHIP. The last Cubs pitcher to lead the NL in WHIP in a season was Fergie Jenkins in 1970 at 1.04.

How does the organization decide where to send players in the Minors? I see they sent Starlin Castro to Double-A Tennessee and Darwin Barney to Triple-A Iowa. Does this mean the front office feels Barney is more ready for the big leagues than Castro? It seems like they call up pitchers from Double-A and position players from Triple-A.
-- Jerry A., Masonville, Iowa

Barney was in Triple-A last year. He did nothing this spring to warrant a demotion, and in fact, impressed the Cubs with his defensive play. If they needed an infielder to sub at the big league level for a short-term callup, Barney could be the guy. As well as Castro has played -- and he's tearing it up at Tennessee, batting .361 -- he only played 31 games there. It's better for him to have success at Double-A and force the Cubs to move him up, rather than be assigned to Iowa at the start of the year, struggle and then be dropped from Triple-A to Double-A.

And a note to Rebel Ridling fans: He was slowed this spring because of health issues but joined Class A Daytona on Tuesday.

I would play Tyler Colvin almost every day. He's a great defensive player, and the Cubs need defense when they're not swinging the bats well. Good defense can inspire good offense.
-- Jeff L., Kenosha, Wis.

Manager Lou Piniella is trying to get Colvin in the lineup as often as he can through his outfield rotation, and it seems to be working. The Cubs have liked what they've seen of Colvin's glove and bat. He nearly hit for the cycle Sunday, and then tripled off a left-hander on Monday.

Is Rudy Jaramillo's hitting program something that could be implemented organization-wise? Has there been talk of doing such? I'm wondering if his approach could be taught to other coaches.
-- Matt W., Atlanta, Texas

Actually, one of the first things Jaramillo did at the Cubs' organizational meetings in November was talk to the Minor League hitting coaches about that. All players in the Cubs system are following Jaramillo's program.