In sports, a lot of bad trades become bad trades after the fact.

The Dodgers’ nine-player trade with the Boston Red Sox in August of 2012 was a bad trade from Day 1.

The Dodgers did the Red Sox a huge favor (and themselves a huge disservice) in the heart of the infamous deal — obtaining Adrian Gonzalez, Carl Crawford and Josh Beckett — and taking on about $260 million in contracts for three guys on the back sides (in two cases, way on the back sides) of their careers.

The Dodgers got 35 starts and a tick over 200 mediocre innings from Beckett before he retired, following the 2014 season.

Crawford, now 34, was a bigger bust — a once-great player in Tampa Bay who had struggled for the Red Sox following their late 2010 signing binge, and who continued to struggle in Los Angeles, where the Dodgers rarely had room for him in their outfield — especially when he flat-lined as a competent ballplayer.

The club designated him for assignment today. Released him, that is.

Crawford was hurt much of his time in Los Angeles and nearly useless when he was active. The club still owes the outfielder $30 million for the 2017 and 2018 seasons. He was a $20-million-a-year-flop in Dodger Blue.

That leaves Gonzalez, 34, as the last man standing from that trade (the Dodgers also got utility man Nick Punto, long gone), and he has been solid in nearly four seasons with the club.

But a solid first baseman is not enough return for the $260 million in contracts the club took on and the two failing veterans they ran out on the field as often as possible.

The Dodgers behaved like sailors on shore leave in that deal, eager to throw away their money, and the Red Sox took full advantage, also getting James Loney and four minor-leaguers.

The Red Sox finished last in the American League East in 2012, but a season later they won the World Series — in part by making a series of astute offseason signings, once they had cleared space on their payroll, in August of 2012, at the Dodgers’ expense.

Ahead of the following season, the unencumbered Red Sox signed Mike Napoli, Shane Victorino, Jonny Gomes and closer Koji Uehara, all key contributors in the turnaround that culminated with the 2013 World Series title.

The Dodgers? They have extended their streak of failing to reach the World Series to 27 seasons, and counting.