NATIONAL HARBOR, Md. — It’s finally happened: The Chicago White Sox have traded ace Chris Sale.

The Boston Red Sox have reportedly struck a deal with the White Sox that will send Sale to the Boston in exchange for infielder Yoan Moncada, pitcher Michael Kopech and two prospects. Ken Rosenthal of Fox Sports was first to report the deal was done. Yahoo Sports’ own Jeff Passan confirmed it too:

The Red Sox paid a pretty penny to get Sale, which everyone knew was necessary to pry him away from the White Sox. The 21-year-old Moncada is considered one of the best prospects in the game. He ranked as the best prospect in baseball on Baseball America’s midseason update in July. Kopech, 20, was limited by injuries last year, but is known for his blazing fastball. He’s hit as high as 105 mph on the radar gun, but is known to have control issues. He ranked 93rd on Baseball America’s midseason update. The Red Sox also gave up minor-league pitcher Victor Diaz and infielder Luis Basabe, according to Dan Hayes of CSN Chicago.

What makes Sale worth all that? Two things: His dominance on the mound and his extremely team-friendly contract. Sale, 27, is a perennial Cy Young candidate who is routinely among baseball’s strikeout leaders. He’s a 6-foot-6 lefty whose three-quarters arm angle makes his pitches difficult to hitters to pick up. If you want to compare him to Randy Johnson, that wouldn’t be wrong — though Sale has actually been better than The Big Unit was at this point in his career.

And about that contract: Sale is under team control until 2020 at a fairly modest rate. The White Sox wisely signed him to a five-year contract extension in 2013 that comes with two team option years. So the Red Sox could keep Sale for $12 million this season, $12.5 million in 2018 and $13.5 million in 2019, all well below market rate.

That, right along with the strikeout totals is what made Sale the most desirable pitcher on the trade market since last summer when his name started to circulate. Inquiries came from all over baseball, but ultimately it was the Red Sox who were willing to give up four prospects to add Sale to the fold.

Now, the Red Sox have to be viewed as the favorite in the AL East, if not the American League as a whole. With a rotation that includes Sale, David Price and reigning AL Cy Young winner Rick Porcello, a group that was ace-less two seasons ago sure seems stacked now.

For the White Sox, the question is now this: Do you tear the whole thing down? Todd Frazier, Jose Quintana, Adam Eaton and Jose Abreu are among the White Sox with trade value. If Moncada is to be viewed as their future star and he’s only 21, the White Sox might see this as reason to extract the value from their roster now and rebuild for a stronger run in three or four years.

Watch for that to be a bigger storyline in the next few days of the Winter Meetings.

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Mike Oz is the editor of Big League Stew on Yahoo Sports. Have a tip? Email him at mikeozstew@yahoo.com or follow him on Twitter! Follow @MikeOz