Why? Because I have the same computer software that Brain and Co. seem to be using for roster management. It's called Sammy Sosa High Heat Baseball 2001 ("SSHH2K1").
In SSHH2K1, Ray Durham is one of the best 2B in the game, a great leadoff man and always a threat to steal a bag. Rich Aurilia is a great player, hitting for power and a good shortstop. I realize the Ginats are playing him at first, but you have to understand that many of the players on the SSHH2K1 Ginats have since retired. So it's getting hard to fill the roster spots with real major leaguers any more. And since all the computer-generated rookies like "Spider Hoover" and "Enrique O'Houlihan" don't pop up in scouting reports Brain is receiving from personnel staff, it's pretty hard to understand what the "reality-centered" scouting community produces, much less those spreadsheet Ivy League nerds. But cheer up- 3B "Jake Smith" is projected to hit 50 HR per year! And "Justin Fuller" might strike out 200 this season!
In SSHH2K1, players age mercilessly, and really tail off in performance after age 34 or so. But there's this great button, "Use 2000 Roster", so that when you start each season players come back just as they were, without the nasty effects of aging! And, since you can simply uncheck the injury box, those players won't ever go down or end their careers prematurely! Robb Nen still shuts them down in the 9th for the SSHH2K1 Giants! Again, this contrasts jarringly with the reports that come from those silly medical staffers who obviously don't realize the capabilities of the software.
Pitching management can be done automatically too, as can all in-game personnel decisions. Nen might pitch three innings, but be unavailable for the next two or three games (there's this irritating "pitcher fatigue" feature that keeps pitchers from appearing more than once every other game or so, you see). And there are useful sliders that control how long starters go, and who pinch hits for whom. Change them during a rainy Dodgers game for extra fun! See Brent Tomko pinchhit! Watch Pedro Feliz play catcher! The "Late Inning Substitution" and "Pinchhitter" sliders are really fun too!!1!!
There's computer control of trades too. You have to be careful here; the computer will trade one or more prospects for your veteran players, even those that are only of marginal utility. So be sure not to mess with those settings or propose trades because the AI is a little sketchy, just let the computer handle the whole thing like the Ginats Brain Trust does.
Finally, there's the most important optional feature. It's called "Computer Management of Minor Leagues". It makes roster moves a snap! The computer figures out which players should be promoted or demoted based on its assessment of their talent. With the click of a button, the "most talented" players at each level will be instantly whisked away to the majors! All the players in AAA that might have had good records? Or the AA performers due to move up? They'll all be cut or stuffed onto the A roster. Soon there'll be 15 players at every level except the majors, and many of the lower-level rosters will be packed with the same players year to year, as the computer instantly and infallibly determines who will never rise above AA ball.
And the computer works during the season too! The 18 year old SS it called up directly from A ball who's batting .100? He'll be sent to AAA for "seasoning" having skipped over a whole level of play, and someone will be called up from A or AA to replace him. And the OF who's batted poorly in 18AB? Off to San Jose with him! There's no waiver wire in SSHH2K1 you see. Move everyone up and down with impunity, whenever the mood strikes you! There's no salary control either, so it doesn't matter what you write in the "salary" blank on the "reality-based" free-agent contracts. The stands are always full, the hot dog and chocolate malt vendors are always hard at work, and the invisible fireworks go off every time Ellis Burks jacks out another dinger!
That's how the computer brain does it, so I understand why the Ginats' "Brain" and the rest of the FO crew does the same. Now you all can relax and enjoy the season! It'll all be done for you, even the boos in the 9th inning when the opposing team piles on a home run in a blowout game.