A short while ago, Ken Rosenthal reported that the Mets will not overpay on Stephen Drew—insiders expect him to return to the Red Sox—and will instead look to trade for a young shortstop. Rosenthal mentioned that the Mets might partner with the Mariners to trade for Nick Franklin or Brad Miller, but the Mariners are still working on a deal for David Price right now and haven't found time to talk to the Mets. Rosenthal also mentions that the Mets may be looking to go after either Chris Owings or Didi Gregorius of the Diamondbacks.
Franklin is considered an average defender at best at shortstop by Baseball Prospectus, but he has a big upside as a hitter. He crushed minor league pitching, but he struggled in his first call-up to the majors with a .225/.303/.382 slash line and a 90 wRC+. Miller performed well in his first major league, hitting .265/.318/.418 with a 106 wRC+, all while playing just-better-than league-average defense.
Regarding the Diamondbacks, Owings hit the ball well for average and played solid defense in a short stint with the big club—.291/.361/.382 and a wRC+ of 106—but seems to lack power. Gregorius seems to be a defense-first player. He had an abysmal call-up with the Reds in 2012, but he was traded to Arizona as part of the Shin-Soo Choo deal and had good defensive year while hitting .252/.332/.373 with a 91 wRC+.
It would seem that both of these clubs present good options for the Mets. All of the aforementioned players are either 22 or 23 years old and displayed a mix of very promising offensive and defensive tools that could certainly be a marked improvement over Ruben Tejada or other internal options.