Ted Williams said hitting a baseball is the most difficult thing to do in an sport---and I totally agree with him. If that's the case, why do batters make it more difficult on themselves with some of the wierdest stances imaginable---like Crawford and Youkilis. Those two will have to adjust as their bat speed slows down with age. I coached for over 30 years and got some insights from men like Joe Gordon (AL MVP, 1942), Sparky Anderson, Ben Hines and o thers. They tried to make a difficult task easier by making it simpler. Moderate stance, maybe slightly closed, elbows and shoulders level, slight bending at the waist toward the plate because that's where your body is heading towards the ball (Ted Williams, Life, 1956). The top of the bat is t ilted towards one or two O'clock in what is called the launch position---Babe Ruth Lou Gehrig, Willie Mays, Hank Aaron and Roberto Clemente to name a few. Then down and through with a quick swing and finishing high. Mays and Ruth had a slight uppercut swing, the ot her three actually hit down on the ball which is what I taught.
You're not going to make a good hitter out of a bad one but you can improve a weak hitter to a point with some good mechanics, something Youkilis along with Crawford are going to have to adjust to as their bat speed slows down with age.