At first glance, this seems like a foolish move, but evaluating the following:
1) He’s been extended at $5M for next season, a bargain (for suitors) if he produces at his 2012 level.
2) He is 38 years old, so an extension would mean you’re discussing years well into his 40′s.
3) The Mets appear nowhere near ready to compete in the NL East.
4) He has exactly 2 season with 10 wins or more.
5) He currently pitches in the pitcher-friendly Citi Field
If the Mets were to get just about anything under the age of 30 or a couple of good regulars (for their depleted lineup) it’s not a bad thought. And a contender in need of a starter (and who isn’t) could use a weapon like this to riddle opponents.
One note about his age, knuckleballers have pitched well into their 40′s in the past (Perry, Niekro for instance) so even extending for 3 or 4 years beyond this isn’t necessarily a bad deal. But I would be hesitant to overpay for someone who might lose the feel for the pitch and vastly underachieve.