As per Nick Cafardo's Sunday column in the Boston Globe, Jon Lester has "been on the Pirates' radar" along with the usual suspects of Zack Greinke, Cole Hamels, Matt Garza, and Ryan Dempster. Carfardo goes on to say that, "It doesn’t appear the Sox would deal unless they got exceptional value back, and it doesn’t appear the Pirates would part with pitching prospect Gerrit Cole, whom the Sox would want."
Lester, 28, is a left-hander that has a triple pitching slash line in 2012 over 112 IP of 4.49 ERA/3.58 FIP/3.61 xFIP, good for a 2.5 WAR to this point. As you can see, he may be getting a tad unlucky, as his ERA is 0.91 runs above his FIP. His K/9 rate is down significantly in the last couple of years -- from 9.74 in 2010 to 7.53 in 2012.