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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. Below are the middle-of-the-rotation starters, which I view as a No. 3 or No. 4 starter on a contending team and, for example, what Diamond seems likely to be long term if things go well and what new Cubs signee Scott Baker was before elbow surgery.

• Shaun Marcum - RHP - 124 innings - 3.70 ERA - 4.21 xFIP - 109/41 K/BB

Marcum never threw hard, but has topped out in the high-80s since returning from Tommy John surgery in 2010. Despite that he has a 3.62 ERA and above-average strikeout rate in 520 innings during that time, thanks largely to a great changeup. After staying mostly healthy in back-to-back seasons Marcum again had elbow issues in 2012, but he pitched well in September. He's a prototypical Twins pitcher and the injuries could drop Marcum into their price range.

• Brandon McCarthy - RHP - 111 innings - 3.24 ERA - 4.23 xFIP - 73/24 K/BB

A former top prospect repeatedly derailed by injuries, McCarthy finally got healthy and thrived for the A's before a second straight strong year was ruined by a line drive to the head on September 5 that led to brain surgery. Obviously his health is a serious question mark and McCarthy isn't as good as his numbers looked in pitcher-friendly Oakland, but he's a solid 28-year-old starter who fits the Twins' strike-throwing mold and is someone to root for on and off the field.

• Joe Blanton - RHP - 191 innings - 4.71 ERA - 3.39 xFIP - 166/34 K/BB

Blanton missed most of 2011 with an elbow injury and on the surface his return was ugly with a 4.71 ERA and 29 homers in 191 innings, but his secondary numbers were far better. Not only were his 7.8 strikeouts per nine innings a career-high, Blanton had the NL's second-best strikeout-to-walk ratio and his 3.39 xFIP ranked 16th in MLB. At age 31 he's not really a breakout candidate, but Blanton is a strike-thrower with more upside than his ERA suggests.

• Kyle Lohse - RHP - 211 innings - 2.86 ERA - 3.96 xFIP - 143/38 K/BB ratio

Lohse was his usual mediocre self for the first five years after the Twins traded him in 2006, posting a 4.66 ERA in 665 innings, but during the past two seasons he had a 3.11 ERA in 399 innings for the Cardinals while starting seven playoff games. At age 34 and with significantly less impressive secondary numbers Lohse is a good bet to be among the offseason's most overpaid free agents, but even if he were available cheaply a Twins reunion would never happen.

• Francisco Liriano - LHP - 157 innings - 5.34 ERA - 4.14 xFIP - 167/87 K/BB

Speaking of unlikely reunions, Liriano is a free agent after the Twins traded him to Chicago for a pair of non-prospects in July. He was the same occasionally dominant but mostly frustrating guy in Chicago, tossing 57 innings with a 5.40 ERA and rates of 9.2 strikeouts and 5.1 walks per nine innings. For the Twins he had a 5.31 ERA, 9.8 strikeouts, and 5.0 walks. At age 29 and with all those strikeouts Liriano has more upside than most on this list, but ... who knows.

• Brett Myers - RHP - 65 innings - 3.31 ERA - 3.92 xFIP - 41/15 K/BB

In both 2008 and this year Myers was shifted from the rotation to the bullpen and made a closer, with strong results, but he's also been a quality starter for most of his career. He has 247 starts with a 4.27 ERA and 7.2 strikeouts per nine innings, including a 3.79 ERA and 340/123 K/BB ratio in 440 innings between 2010 and 2011. As a fly-ball pitcher he struggles to limit homers, but Target Field would help that if the Twins are willing to bring in a not-so-wonderful person.

• Roy Oswalt - RHP - 59 innings - 5.80 ERA - 3.27 xFIP - 59/11 K/BB

Oswalt talked about retiring because of back problems, sat out the first two months before signing with the Rangers, and then got knocked around for a 5.80 ERA while being demoted to the bullpen. At age 35 he may simply be nearing the end of the line, but a 59-to-11 strikeout-to-walk ratio in 59 innings suggests Oswalt wasn't nearly as bad as his ERA. His velocity was the same as 2011, when he pitched well for the Phillies, and his track record is tough to beat.

• Carlos Villanueva - RHP - 125 innings - 4.16 ERA - 4.09 xFIP - 122/46 K/BB

Villanueva had a lot of success as a starter in the minors, but has spent most of his big-league career as a long reliever and has been mediocre when called on to make spot starts. He started 16 times for Toronto in 2012, struggling to keep the ball in the ballpark while posting a 4.50 ERA, but also had an 86-to-25 strikeout-to-walk ratio in 92 innings. If given a chance to build up his arm strength as a full-time starter at age 29 he could provide nice value.

• Erik Bedard - LHP - 126 innings - 5.01 ERA - 4.05 xFIP - 118/56 K/BB

He's basically never stayed healthy, has a reputation for being a pain in the ass, and posted a 5.01 ERA for the Pirates this year, but Bedard's superior secondary stats included 118 strikeouts in 126 innings. And during the previous five years his worst ERA was 3.76 and his worst strikeout rate was 7.8 per nine innings. I'd never invest big money or multiple years in Bedard, especially at age 34, but for the hope of 25 starts on a one-year deal he's got some bat-missing upside.