The Major League Baseball trade deadline date was on June 15 from 1923 through the 1985 season before switching to it’s current July 31 date beginning in 1986.

Multiple trades have been made by the New York Mets on this date, some that ended up helping the team tremendously and one that most consider the worst in franchise history.

1969

The Mets entered deadline day 30-25, 8.5 games behind the Chicago Cubs for the East division lead and in need of depth. The Mets swung a deal to send infielder Kevin Collins and three minor leaguers Steve Renko, Jay Carden and David Colon to the Expos for first baseman Donn Clendenon.

Clendenon would hit .252/.321/.455 with 12 home runs in 72 games with the Mets on their way to winning the National League East over the Cubs by eight games.

The right-handed hitter would save his best for the World Series in 1969. He went 5-for-14 with three home runs as the Mets beat the Baltimore Orioles for their first ever championship. Clendenon won the World Series MVP for his impressive performance.

Clendenon followed his postseason heroics with one of the best seasons of his career in 1970 when he hit .288/.348/.515 with 22 homers, 97 RBI and finished 13th in regular season MVP voting. He would hit 11 more home runs for the Mets in 1971 before being released by the team at 35-years-old.

1977

This deadline was much different with a Mets team heading in the opposite direction of the 1969 Mets. They were 25-35 on the deadline and 14 games away from the league division lead.

June 15, 1977 will forever be remember by Mets fans as the Midnight Massacre with New York trading a few core pieces including the disgruntled Tom Seaver.

Seaver was went to the Cincinatti Reds for Doug Flynn, Steve Henderson, Dan Norman and Pat Zachry. Seaver was fantastic to finish the season going 14-3 with a 2.34 ERA in 20 games with the Reds. The Franchise would pitch five more seasons in Cinci including two All-Stars appearances and finished Top 5 in the CY voting twice.

Flynn was a defensive gem at second base for the Mets including a Gold Glove award in 1980. Henderson would finish the 1977 season hitting .297/.372/.480 and came in second in the NL Rookie of the Year voting. After three more seasons with the Mets he was traded for Dave Kingman in 1981. Norman posted a -0.5 WAR in four seasons with the Mets before getting shipped with Jeff Reardon for Ellis Valentine in 1981. Zachry went 41-46 with a 3.63 ERA in six seasons for the Mets before he was traded in 1982 for Jorge Orta.

The Mets also traded slugger Dave Kingman to the Padres for left-handed pitcher Paul Siebert and utility guy Bobby Valentine. Siebert was traded to the Cardinals for Bob Coluccio after just 56 innings with the Mets. The defensive minded Valentine had a .575 OPS in 111 games with the Mets before being released in 1979. Kingman would of course return to the Mets in the previously mentioned traded of Henderson.

The third trade of the that day in 1977 worked out pretty well for the Mets when they acquired infielder/outfielder Joel Youngblood from the Cardinals for light-hitting infielder Mike Phillips. Youngblood would hit .274/.333/.410 in six seasons with the Mets before he was traded to the Expos in 1982.

1979

The Mets traded for veteran pitcher Dock Ellis. They sent pitchers Mike Bruhert and Bob Myrick to the Rangers for Dock. With his best days behind him Dock didn’t fare well for the Mets going 3-7 with a 6.04 ERA in 17 games.

1983

The Mets made arguably one of the best trades in franchise history on this date in 1983 when they sent pitchers Neil Allen and Rick Ownbey to the Cardinals for slick fielding first baseman Keith Hernandez.

Cardinals were coming off a World Series win in 1982 and Keith had won his five straight Gold Gloves. Keith had also finished in the top 20 of MVP voting four straight seasons including sharing the award with Willie Stargell in 1979.

Keith was dealt in part because he was a pending free agent following the season but Cards manager Whitey Herzog also said late in his book that Hernandez was “dogging it” and “I couldn’t live with his attitude.”

Hernandez would be an All-Star, Silver Slugger, Gold Glover and finished second in MVP voting his first full season with the Mets in 1984. Two years later, Kieth was an integral part of the Mets 1986 World Series champsionship team hitting .310/.413/.466 during the regular season and finished fourth in MVP voting.

In parts of seven seasons with the Mets, Hernandez hit .297/.387/.429 with three All-Star appearances, six Gold Gloves and amassed 26.6 WAR. That 26.6 WAR ranks 11th all-time in Mets franchise history.