He's also, as far as anyone knows, never been a heavily relied upon starting pitcher at the Major League level at any point of his life, either. Really, all pitchers have flawless injury records until they start to break down. Mark Prior had "perfect mechanics" and (IIRC) a spotless medical history at the amateur level but that didn't translate into sustained success when he made the jump to the Majors.
There has never bee never been a question of Sale's ability but he will continue to be hounded about his durability for at least a few more seasons.
Granted, I only became a rabid Sox fan around the 92/93 season and then my family didn't have cable until around 2000 so I don't remember McDowell all that well, but while the frame may have been similar, just a basic Google Image search shows different mechanics for them... Sale pitches with the feared Inverted W, pretty much every image I can find of McDowell doesn't fit that...
That's not the Inverted W and, as far as I am aware, the current consensus is that mechanics are far more important than frame in determining the likelihood of injury.
And really, at any rate, McDowell was an OUTSTANDING
pitcher through his 20's, and even was an AL-average innings eater through his mid-30's (I know his raw numbers are a bit inflated, but those were the height of the Steroid Era/Juiced Ball offensive explosion, he never posted an ERA+ under 90 until his final season when he threw a grand total of 19 innings over 4 starts). The only reason his career ended at 33 was due to a botched surgery. This is still a guy who earned 25.1 WAR for pitchers over his career (a hair outside the Top 300 P of all-time
), won a Cy Young Award, pitched in 3 All-Star Games. If that's the career course Sale will be on, that's not exactly something to sneeze at.
Sale is going to turn 24 years old just before the 2013 season starts. He hits arbitration for the first time next off-season and can become a free agent after the 2016 season, when he will be 27 years old. If the Sox could find a way to buy out some arb years and maybe lock him up for an extra year or two, I'd be willing to do that. But you also got to remember that Sale took a bit under what he was asking for after the Sox drafted him based on the promise that they would fast track him to the Majors and start his arb clock as soon as possible. You got to wonder how much more charity he's willing to give.