Sergio and Clarke and Montgomerie and Westwood are all chokers in the majors. The same thing that helps them in the Ryder Cup, namely playing on emotion, kills them in major championships. Stroke play in extremely difficult conditions over four days requires a certain degree of singleminded focus and the ability to block out highs and lows.
Not saying that a guy like Sergio will never win a major, but look at the guys who have won in recent years. Tiger is a robot who spits out the occasional F-bomb. Ben Curtis, Hamilton, Micheel, Olgilvy, Weir, Toms, Furyk, etc. Non are what you would call exuberant personalities. There will always be the exception—the John Daly pumping his fist walking up the 18th firing up the crowd—but I would usually favor the guy who can suppress/conquer his emotions.