BOSTON -- BASED on what General Manager Ben Cherington has said, and what the other options would be, it’s fairly certain that no matter how mediocre his own numbers may be, Kevin Youkilis’ Sox would still be red instead of white had Will Middlebrooks not used the first quarter-season of his career to prove he’s ready to be an everyday major-league third baseman.

That’s essentially what the 23-year-old became Monday night, batting sixth and stationed at the hot corner, where the expectation is he’ll remain for the better part of the coming decade. But Sunday’s trade of Youkilis to Chicago isn’t only a tipping point in the transition from past to future at a single position. It underscores that such a transition is under way — and largely complete.

In his first seven months on the job, the Meriden-born Cherington has separated the Sox from franchise icons Tim Wakefield, Jason Varitek and now Youkilis, leaving nostalgia for the centennial celebration of his home ballpark, and making obvious that it has little place in his effort to build the ballclub that plays therein.

All three won two World Series rings in Boston, and without Youkilis gone, David Ortiz becomes the only active Red Sox who can make such a claim. But understanding the transition doesn’t require going back as far as 2004.

The Red Sox now employ only five members of the 2007 title winners — Ortiz, Dustin Pedroia, Jon Lester and Daisuke Matsuzaka, as well as the currently disabled Josh Beckett, Clay Buchholz and Jacoby Ellsbury — and Buchholz wasn’t even with the team that postseason or the next. That means only six members of the current club have won a playoff game with the organization, and only two of them played Monday.

With so much turnover on the field, plus a new manager and general manager in place, it’s impossible to think the clubhouse isn’t a different place than it was five years ago. In fact, it’s well on its way to being different than it was just one year ago.

After Youkilis’ exit, only 13 of the 25 players active for the Sox on Monday were participants in the worst September collapse in baseball history. And those guys accounted for just 105 1/3 of the 243 innings pitched, and 113 of the 243 games started by batters. Surely, some of that is the product of an overloaded disabled list, but not all. Only 19 of the 46 players on Boston’s roster appeared in a game last September.

The question now, of course, is how much longer the rest of them remain. The haul Cherington got in return for Youkilis suggests the deal was done with this season still in focus, adding utilityman Brent Lillibridge — who inherited Youkilis’ locker stall upon his Monday arrival — and Zach Stewart, a 25-year-old pitcher who’s been traded three times in three years. The ex-Fisher Cat has upside, but has yet to show evidence that he’s a building block.

There could be more moves to follow before the trade deadline that looms about a month from now, the nature of which will likely be dictated by how Boston’s nine plays between now and then. But whatever that maneuvering may entail, it’ll only amount to more evidence that the Sox are moving forward.

They’re a team that happily started three players wearing numbers in the 60s on Monday night. They’re a team that had about $75 million worth of veteran talent on the disabled list, and was paying $5 million to the guy batting second in Chicago, and still there was something to like about the energetic composition of the roster. They’re a team with the reigning American League Player of the Week at third base, that award recognizing a start that’s been of Albert Pujols-esque proportion and prompted the move that made the transition plain for all to see.

There was still evidence of the old guy at the park Monday. In the second inning, footage of Youkilis’ emotional Sunday sendoff was incorporated into a scoreboard video package featuring former Red Sox greats. And before the game, on a walk outside the park, the first jersey a reporter spotted on a fan was that of the ex-No. 20.

The second, incidentally, was that of Trot Nixon. Call it evidence that the past always seems a little bit sweeter than the present.

For the Red Sox, though, it’s now on to the future.

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WITH YOUKILIS in Chicago, Beckett becomes the second-longest tenured Red Sox player — and he may join the active ranks again by the end of the week. Out since June 12 with right shoulder inflammation, a recent bullpen session went well enough that the righty could return as soon as Friday in Seattle.

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ORTIZ’S first-inning homer was his 19th of the season. Coming on June 25, it’s the third-earliest on the calendar that Ortiz has clubbed that many taters. The earliest came in 2006, when it was hit on June 17; last year, he smacked No. 19 on July 8.

Dave D’Onofrio covers the Red Sox for the New Hampshire Union Leader and Sunday News. His e-mail address is ddonof13@gmail.com.