MLB

OLD PARK’S GOTTA SPAWN NEW ARMS

THE most explicit manifestation of the ongoing old-to-new evolution for the Yankees looms just a long Alex Rodriguez drive to left away. It will be impossible to attend the final home opener of the old Yankee Stadium today without seeing its steel and cement successor almost fully conceived.

It serves as cash cow on the horizon and metaphor of where the Yankees are right now. The Steinbrenners on display amid the Opening Day glitz will be Hank and Hal as they open a first full season as organizational front men while their famous dad fades further into the background.

Meanwhile, the on-field stewardship passes from one Joe (Torre) to another (Girardi) in what feels like the managerial equivalent of the baton pass from the typewriter to the laptop.

Yet it is the transition from old pitching to young that hovers most over this Yankee season; that determines just how gloriously the Yanks will cross the street to that $1 billion-plus mega-facility, how furiously Hank Steinbrenner reacts to the inevitable downturns of a season, and how likely Girardi is to succeed Torre with equal or greater success.

The story of the offseason does not change now that the Blue Jays are here to start the real season. After all the analysis and speculation about Joba Chamberlain, Phil Hughes and Ian Kennedy, we now get to see how Generation Trey handles not only being instrumental to a season-long effort, but pioneers for how the Yankees want to build future pitching staffs.

In George Steinbrenner’s ownership tenure only once have the Yanks used two pitchers 23 or under to each start as many as 20 games. That was 1982, with Mike Morgan and Dave Righetti. The Yanks finished with a losing record for the first time since Steinbrenner’s debut season (1973). Since then, only two other 23-and-under Yankees have been allowed to make 20 starts: Doug Drabek (1986) and Andy Pettitte (1995).

Torre asked a grand total of 40 starts from 23-and-unders in his 12-year term, and now that would feel like a minimum for Girardi in just 2008. It feels as if Girardi has to receive 20-plus starts from both Hughes, who turns 22 in June, and Kennedy, 23, before even contemplating what Chamberlain offers if and when he is steered from the bullpen to the rotation.

“I expect them to be successful this year,” Girardi said.

They must be. The degree of difficulty in the ferocious AL just might be too great for the Yanks should their youngsters not prosper in the rotation. And what does history say of the Yankee chances? In the divisional play era (since 1969) 82 teams have used at least two 23-and-under pitchers to start a minimum of 20 games each in a season. Here are the key results (with age determined by how old the pitcher was on June 30):

* Fifteen such teams reached the playoffs. That does not include the 1994 Expos (Pedro Martinez and Kirk Rueter), who had the NL’s best record when the season was canceled. But it does include a team from each of the past two seasons: the 2006 Tigers (Justin Verlander and Jeremy Bonderman) and the 2007 Phillies (Cole Hamels and Kyle Kendrick).

* Three such teams won championships: The 1985 Royals (Mark Gubicza, Danny Jackson and Bret Saberhagen), the 1986 Mets (Dwight Gooden and Sid Fernandez), and the 2003 Marlins (Josh Beckett and Dontrelle Willis).

* In general, however, the young pitchers on such successful teams have had far more experience going into those campaigns than the combined 912/3 regular-season innings that Hughes and Kennedy have combined. Only two of the 15 cited playoff teams had their 23-and-unders work fewer than 100 career innings each prior to the year in question: the 2003 Giants (Jerome Williams and Jesse Foppert) and the 1970 Twins (Bert Blyleven and Bill Zepp). The quick flameouts of pitchers such as Williams, Foppert and Zepp should be a cautionary tale with the Yanks.

* Girardi has experience in using such inexperience. He asked three 23-and-unders (Rich Nolasco, Scott Olsen and Josh Johnson) to make 20 or more starts for the 2006 Marlins, Girardi’s only previous managerial season. Another 23-and-under, Anibal Sanchez, started 17 games. And Dontrelle Willis, who was just 24, led the team with 34 starts.

* Can growing pains be worth it? The 1989-91 Braves finished last three straight years and averaged 100 losses. But in various permutations they broke in 23-and-unders Tom Glavine, Pete Smith, Derek Lilliquist, John Smoltz and Steve Avery (while the Cubs were breaking in 23-and-under Greg Maddux). That pitching graduate program would provide the backbone, beginning in 1992, for the Braves to reach 14 straight postseasons.

The current Yanks have reached 13 playoffs in a row. To tie the Brave record, the Yanks need their young starters to limit the growing pains and make the final season in the old stadium best remembered for a new arms revolution.

joel.sherman@nypost.com