Left-handed relief pitcher Mike Gonzalez has been in Major League Baseball since 2003, and his career 3.14 ERA, 3.50 FIP, and 10.35 strikeouts per nine are pretty good. Starting with the 2008 season, however, he's been a bit up and down on a yearly basis. In 2013, he pitched to a 4.68 ERA and 4.87 FIP with the Milwaukee Brewers, well below league average for a relief pitcher by either metric.
In 2012, Gonzalez fared much better as he pitched for the Nationals. In 47 appearances totaling just 35.2 innings, Gonzalez had a 3.03 ERA and 2.98 FIP. He was dominant against left-handed hitters that year, which has generally been the case over his career.
Entering his age-36 season, the most concerning thing about Gonzalez might be that his fastball has lost a bit of velocity over the past couple of seasons and averaged 91.2 miles per hour in 2013. That's not slow, but it is down a bit from the 92-to-93 range he had from 2007 through 2011. He's had a history of injuries, too, with Tommy John surgery back in 2007 and knee surgery in 2011, among other things. Despite that, he's averaged 54 appearances per season since returning in 2008.
A Gonzalez signing might not be exciting, but if the Mets could bring him in on a low-cost deal, it wouldn't be a bad move. He's always struggled with walks, but there's a decent chance he could at least match the production that Tim Byrdak gave the Mets in a lefty specialist role between 2011 and 2012.