Throughout July we're going to present 30 deals in 30 days: The best trade deadline deal ever made by each team. We've covered the AL East so far and are now on the NL East.

THE TEAM: New York Mets

THE YEAR: 1983

THE SITUATION: The Cardinals were the defending World Series champs and were leading the NL East by a game on June 15 despite a rotation that was struggling, especially ace Joaquin Andujar (he would finish 6-16 with a 4.16 ERA after going 15-10, 2.47 in 1982). What was really upsetting manager Whitey Herzog was the play of first baseman Keith Hernandez. Herzog would later write in "White Rat: A Life in Baseball":

Keith Hernandez was dogging it. ... He's the best defensive first baseman I've ever seen. But on offense, he was loafing. He loafed down the line on ground balls and he wasn't aggressive on the bases.

What I couldn't live with was his attitude. I've got two basic rules -- be on time and hustle -- and he was having trouble with both of them. ... His practice habits were atrocious. He'd come out for batting practice, then head back to the clubhouse to smoke cigarettes and do crossword puzzles. ... It was getting to the point where I was fed up with him.

Hernandez was also an impending free agent ... and also using cocaine, which Herzog didn't know for sure but wrote that he suspected might have been the case. (Hernandez would later testify that he ended his habit just before the trade to the Mets.)

So the Cardinals needed pitching, Herzog wanted to get rid of Hernandez, and they also wanted to make room for young outfielder David Green (they could shift George Hendrick to first base).

THE TRADE: On June 15 -- the trading deadline back in 1983 -- the Cardinals shockingly traded Hernandez to the Mets for right-handed pitchers Neil Allen and Rick Ownbey. Cardinals fans booed when the deal was announced right before that night's game. Allen was the key to the deal, a 25-year-old reliever with a good arm whom Herzog wanted to try as a starter. Hernandez reportedly had blocked a trade to the Astros for Ray Knight.

THE AFTERMATH: Allen would go 10-6 with a 3.70 ERA for the Cardinals, but they would fade after the deal and finish 79-83. Allen would be returned to the bullpen in 1984 and then traded to the Yankees in 1985. Green never did develop into the star Herzog projected.

Hernandez, hitting .284 with three home runs in 55 games at the time of the trade, would rediscover his swing in New York (wild guess: quitting coke helped). He hit .306 with nine home runs the rest of the season, although the Mets were awful and finished 68-94. But in 1984, they would hire Davey Johnson as manager and insert rookies Dwight Gooden and Ron Darling into the rotation. In 1985, they'd trade for Gary Carter. In 1986, they'd win the World Series.

During his four-year peak with the Mets, 1984 to 1987, Hernandez hit .305 with a .396 OBP and finished second and fourth in the MVP voting in 1984 and 1986, respectively. Baseball-Reference credits him with 20.2 WAR those four seasons, 13th-best in baseball among position players.