AaronGleeman.com

Twins starting pitchers combined for a 5.00 ERA during the past two seasons to rank dead last in the league and they head into the offseason with only Scott Diamond locked into a rotation spot. Terry Ryan has said he'd prefer to address the rotation via trades, which is no surprise for a team that's basically never pursued free agent pitching beyond bargain-bin shopping, but if they do decide to dive into the free agent pitching pool the water is reasonably deep.

In an effort to figure out the Twins' options I've separated the free agent pitching class into three categories: Top-of-the-rotation starters, middle-of-the-rotation starters, and back-of-the-rotation starters. First up are the top-of-the-rotation starters, which I view as a No. 1 or No. 2 starter on a contending team. By definition there are only around 40 of those guys across baseball, but a half-dozen of them are hitting the open market at the same time.

• Zack Greinke - RHP - 212 innings - 3.48 ERA - 3.22 xFIP - 200/54 K/BB

As a 29-year-old coming off an excellent season and the only true ace available Greinke should be way out of the Twins' price range even if perceived off-field issues cause some teams to shy away. Greinke won the Cy Young award in 2009 and in the three seasons since then he ranks among MLB's top 10 in strikeout rate and strikeout-to-walk ratio while placing fourth in xFIP behind only Cliff Lee, Roy Halladay, Adam Wainwright, and Felix Hernandez.

• Anibal Sanchez - RHP - 196 innings - 3.86 ERA - 3.60 xFIP - 167/48 K/BB

Sanchez recovered from multiple arm surgeries early in his career to throw at least 195 innings in each of the past three seasons and he's still just 28 years old. While not overpowering, Sanchez's above-average raw stuff produced 8.1 strikeouts per nine innings from 2010-2012 and he fared well for the Tigers after leaving the NL for the first time. Among all MLB starters since 2010 he's 26th in xFIP and 35th in ERA, which is a strong No. 2 starter.

• Dan Haren - RHP - 177 innings - 4.33 ERA - 4.00 xFIP - 142/38 K/BB

Haren has long been one of MLB's most underrated pitchers, posting a 3.48 ERA with fantastic strikeout-to-walk ratios from 2005-2011 and topping 200 innings every season. Back problems in 2012 limited him to 177 innings and a 4.33 ERA that's the worst of his career, with the Angels choosing a $3.5 million buyout instead of a $15.5 million option. If healthy Haren could be a major bargain and a fly-balling fit for Target Field, but at age 31 a long-term commitment is risky.

• Edwin Jackson - RHP - 190 innings - 4.03 ERA - 3.79 xFIP - 168/58 K/BB

After failing to land a huge contract as a free agent last offseason Jackson opted for a one-year, $11 million deal from the Nationals and hits the open market again sans qualifying offer. His numbers were similar to 2011, so I'm curious to see if the demand is higher this time. Jackson's overall production and strikeout rates have never quite matched his raw stuff, but he's started at least 30 games in six straight seasons despite being just 29 and ranks 36th in xFIP since 2010.

• Hiroki Kuroda - RHP - 220 innings - 3.32 ERA - 3.67 xFIP - 167/51 K/BB

Kuroda was billed as a mid-rotation starter when he came over from Japan in 2008, but he's pitched like an ace with a 3.48 ERA in 919 innings. That includes a 3.32 ERA and 167/51 K/BB ratio in 220 innings for the Yankees, transitioning smoothly from a pitcher-friendly NL ballpark to a hitter-friendly AL home at age 37. He likely has no interest in pitching for the Twins and after receiving a qualifying offer it's probably a moot point anyway.

• Ryan Dempster - RHP - 173 innings - 3.38 ERA - 3.77 xFIP - 153/52 K/BB

It was odd to see so many people buy into the notion of Dempster as an elite starter around the trade deadline. He had a pretty 2.25 ERA, but it was only 16 starts from a 35-year-old with a 4.09 ERA in the previous three years. Dempster was traded from the Cubs to the Rangers and came back down to earth with a 5.09 ERA in 12 starts. He's often pitched like a borderline No. 2 starter, but his velocity is trending in the wrong direction to feel good about a multi-year deal.