Anthony Rieber Newsday columnist Anthony Rieber

Anthony Rieber has been at Newsday since Aug. 31, 1998 and in his current position since 2004.

Yoenis Cespedes may not -- and should not -- win the NL MVP award this season. But the slugger's amazing stint with the Mets may earn him another title: The best in-season pickup in franchise history.

Cespedes, who is batting .283 with 17 home runs and 42 RBIs in 45 games since joining the Mets in a trade with Detroit on July 31, is the most recent star to be acquired by the team during the season and make a huge impact.

The list begins with Donn Clendenon, who was traded to the Mets in June 1969 and went on to win that year's World Series MVP.

It continues with Keith Hernandez, whom the Mets picked up from the Cardinals in June 1983. Hernandez became a Mets icon -- he still is as a broadcaster -- and led the team to its last World Series title in 1986.

The Mets traded for Mike Piazza in May 1998. Like Cespedes, he was in the last year of his contract, and it was unclear if the Mets were going to re-sign the All-Star catcher. They ultimately did, and Piazza became one of the pillars of the 2000 World Series team.

What Cespedes has done so far in his brief Mets career has been astounding. The rest of the story -- from the Mets' probable postseason appearance to Cespedes' future with the team, if any -- has yet to be written.

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But that didn't stop us from reaching out to WOR 710 Mets broadcaster and noted team historian Howie Rose (author of "Put It in the Book! A Half-Century of Mets Mania") to ask this simple question: at this point, which of these four is the best in-season pickup in franchise history? Howie gives his pick. What's yours?

DONN CLENDENON

Trade: Acquired from the Montreal Expos on June 15, 1969 for Steve Renko, Jay Carden, David Colon, Kevin Collins and a player to be named later (Terry Dailey)

Mets tenure: 1969-71

Mets stats: .267, 45 HRs, 171 RBIs in 281 games (regular season)

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Highlight: World Series MVP in 1969

Howie's take: "I think Clendenon has been practically canonized over the 46 years since he was traded here because of how it ended. If you look at Clendenon's numbers, they were good, but they didn't approach anything that Cespedes is doing. [Clendenon] hit three home runs in the World Series, he won MVP, and that obviously earns him a very special place in this franchise's history."

KEITH HERNANDEZ

Trade: Acquired from the St. Louis Cardinals on June 15, 1983 for Neil Allen and Rick Ownbey

Mets tenure: 1983-89

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Mets stats: .297, 80 HRs and 468 RBIs in 880 games (regular season)

Highlight: Leader of Mets mid-80s renaissance

Howie's take: "Keith changed everything. The ramifications of Keith's arrival transcended the year he came here. Frankly, it still lives today based on his legacy and the standard that he established for leadership, for how to play the position. He changed the culture. That's kind of the cliche now, but he was central to changing that culture and had an impact for years. That's why he's at the very top of that list. He's the gold standard."

MIKE PIAZZA

Trade: Acquired from the Florida Marlins on May 22, 1998 for Preston Wilson, Ed Yarnall and Geoff Goetz

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Mets tenure: 1998-2005

Mets stats: .296, 220 HRs, 665 RBIs in 972 games

Highlight: Led Mets to World Series in 2000

Howie's take: "Piazza was somewhat different because he wasn't a trade-deadline deal and when they brought him on there was a little caveat because he could have left at the end of the year as a free agent. He never went on a run that year like Cespedes has. No one has had a run like Cespedes has. But when you look at Piazza's impact on the organization over the seven years he was here, it's not far behind Keith's, in my opinion."

YOENIS CESPEDES

Trade: Acquired from Detroit Tigers on July 31, 2015 for Michael Fulmer and Luis Cessa

Mets tenure: 2015-TBA

Mets stats: TBA

Howie's take: "For all that Mike accomplished, for all that Keith accomplished, that was over years. I've never seen anything like this. Never. Not from a Met, anyway."