Between Luis Castillo's bad performance and yearn to start, as well as the injury and potential surgery to top MI prospect Reese Havens, It seems pretty clear to me that the Mets are (and should) be very active on the free agent market for second basemen. The budget allows for very little flexibility, with the absence of John Maine, Jeff Francoeur, Rod Barajas, Alex Cora, Pedro Feliciano and Fernando Tatis being replaced by pay raises to David Wright, Jose Reyes, Johan Santana and Jason Bay. Presumably Angel Pagan as well. With this in mind, the Mets will likely look to dump current second baseman Castillo somewhere before making any transactions for his replacement.
Finding a team to take on Luis Castillo and at least some of his contract (because that's all the organization is really worried about...) will be no easy task. This is the common knowledge for both Mets fans as well as the rest of baseball. Castillo isn't very good. On the other hand, Castillo really isn't as bad relative to his position as one might think he is. The following players make up this year's free agent class at second base:
Willie Bloomquist (33)
Mark Ellis (34) - $6MM club option with a $500K buyout
Bill Hall (31) - $9.25MM club option with a $500K buyout
Orlando Hudson (33)
Omar Infante (29) - $2.5MM club option with a $250K buyout
Akinori Iwamura (32)
Adam Kennedy (35) - $2MM club option
Felipe Lopez (31)
Julio Lugo (35)
Outside of Mark Ellis, Juan Uribe and Orlando Hudson, we see a whole pile of nothing. The only credible players outside of those two are Omar Infante and Adam Kennedy, both with extremely affordable team options. The rest are replacement level, or incredibly volatile, such as Felipe Lopez or Jose Lopez.
Castillo is actually a more attractive option then most of the market. If the Mets offer to take on half his contract he can be had essentially for free on a 1-year $3 million deal to any team that takes him. He walks a lot, strikes out very little, and most importantly showed defensive value in 2010 according to both UZR and Total Zone, which put him right in the middle of the pack in second basemen. Teams like to know what they're buying, and in this case they have that in Luis Castillo. The Padres, Twins, A's, Tigers, Royals, Rockies and Cardinals are all rather weak at second base, so they may take flyers.
With Castillo leaving, the Mets do not necessarily HAVE to turn to the free agent market to replace him. The newly-acquired Justin Turner, who is by no means automatically a AAAA player, has had success all throughout the minors with the bat, and will be 26 at the start of next year. He has had no success in his 40 MLB at-bats, but if he can even SOMEWHAT replicate his minor league offensive numbers, he is a weapon. Ruben Tejada can play a pretty good defensive second base, but his bat is very questionable. Daniel Murphy has been the general cry amongst Mets fans for a while, and he was trying out the position before acquiring a season ending injury. At the end of 2009 Murphy began to rap pretty well, and also showed some pretty good athleticism at first, however his long time without playing and lack of experience arouses skepticism.
No internal option is ESPECIALLY attractive, but a Murphy/Tejada platoon or giving Tuner the position is a possibility.
This leaves the Big 3 in the free agency: Mark Ellis, Juan Uribe, and Orlando Hudson.
Mark Ellis has been a career long Athletic, starting pretty much his entire career due to his superior defense. His bat comes and goes, but his incredible talent for the position keeps him valuable. He will be 34 in 2011. His defense would be a solid addition to the Mets team, as most of the pitchers on the Mets' staff do not have high strikeout numbers. However; his lack of hitting value doesn't help the Mets offense, which has been one of the worst in baseball. By no means is he a bad signing. If he can be had on a 1 year deal worth $4-5 million, it's worth looking into at the very least. His presence could definitely up the value of Pelfrey and Dickey.
Juan Uribe was once a top prospect in the Rockies organization. He's an athletic free-swinger who hits for power and is more than competent at just about any infield positions. His all-or-nothing approach at the plate is his downfall. He often pops out or hits weak ground balls, and walks minimally. He struggled at the White Sox starting shortstop, and was picked up by the San Francisco Giants on a 2-year deal. Since then, Uribe's value has gotten significantly higher. 2009 was the best offensive season he's had since his rookie season, and in 2010 he had a career-high walk rate and hit 20 homers. Uribe has shown defensive prowess at second base, third base, as well as shortstop, and his pop would be welcome in the Mets lineup, if Citifield doesn't take it away, that is. At his best, Uribe can be an MLB regular at 2B, 3B or SS. At worst, he is a useful bench player. Getting Uribe on a 2-year deal would be a good risk/reward move by the Mets.
Orlando Hudson is the most popular option amongst Mets fans it seems. He has signed reasonable contracts throughout his career, he can play second base very well defensively, and he isn't a slouch with the bat either. Hudson has signed a pair of 1-year deals through 2009 and 2010, and getting him on one would certainly be a good add for the Mets to bolster their second base position, which has never really gotten any value outside of Jose Valentin's fantastic surprise 2006, since Edgardo Alfonzo manned the position. Hudson's offensive value doesn't include hitting for power, so Citifield most likely won't diminish it, and the move back to the National League should up his offensive numbers a bit.
All three free agent second basemen would be pluses for the Mets, who need any upgrade they can get with the absence of Johan Santana.