Whether or not you agree with the Mets’ decision to retain Marlon Byrd at yesterday’s trade deadline, there’s no disputing that Byrd and Eric Young Jr. have made valuable contributions to the occasionally entertaining/competent 2013 ballclub, and both were acquired at minimal cost.  And while GM Sandy Alderson deserves full credit for those moves, it’s also worth remembering that not every veteran addition has paid off ; in fact, there’s one who continued to do damage to the parent club long after he was no longer on the roster.  Consider the following passage from the New York Daily News’ Andy DiMartino in the midst of a Tuesday profile of P Jenrry Meijia (link swiped from Metsradamus)

Once the organization’s top pitching prospect, he had become a nearly washed-up 22-year-old with nothing in his toolbox — a low-90s fastball with no movement, and secondary pitches that weren’t fooling anyone. Then, in a side-session last September, the pitching coach made a career-reviving suggestion.

“When I came here in September last year, Dan Warthen showed me how to throw a slider,” said a beaming Mejia, back in a major league clubhouse. “Then I threw it in winter ball. And now I throw it perfect.”

That might read like a boast, but he said it with glee, not swagger.  After posting a 5.62 ERA last September, then missing most of the first half this year with discomfort in his forearm and elbow (he needs offseason surgery, but does not consider it major), Mejia seemed cooked for good.  And, according to organizational sources, he had Frank Francisco advising him to stay in Port St. Lucie and collect his big league D.L. money, rather than work to return and be optioned to the minors.