Generally speaking, teams prefer pitchers who get ground balls. Ground balls can sneak through the infield for base hits, but they never go over the fence for a homer and need to be well-placed (down the line, typically) to go for extra bases at all. Great pitchers like David Price, Felix Hernandez, and Clayton Kershaw get both strikeouts and grounders, but few can do both.
The MLB average ground ball rate was 45.1% in 2012, the highest it's been since reliable batted ball data started being recorded in 2002. Trevor Cahill led all qualified pitchers with a 61.2% ground ball rate this past year, and he was the only pitcher over 60%. Phil Hughes had the lowest ground ball rate at 32.4%, making him one of only two pitchers below 35% (Bruce Chen, 32.7%). Here's the short list of unsigned free agent pitchers who posted a better than league average ground ball rate last season (min. 80 IP)...
Kevin Millwood (44.7%) fell just short of a league average ground ball rate while both Erik Bedard (43.3%) and Joe Saunders (43.1%) were a little further behind. Kyle Lohse, the best starting pitcher left on the market, generated a ground ball 40.5% of the time this past season. Shaun Marcum is a big time fly ball pitcher, with a 35.4% grounder rate in 2012 and a sub-41% rate in four of his five full big league seasons.
It's worth noting that Carl Pavano, who didn't pitch much in 2012 due to a shoulder problem, had a 50.6% ground ball rate in 2011. Brett Myers, who is looking for a job as a starter, posted a 47.7% ground ball the last time he was a full-time rotation guy.