Steve,
There is no magic wand that will eliminate the influence of "nerves", however, the long putter reduces the influence of nerves for many, ergo it's popularity.
Using the long putter is cumbersome and unnatural, yet, it's becoming more popular because of it's ability to ameliorate the influence of nerves.
Scott's 4 finishing bogey's were more a product of his thinking, club selections and ball striking.
When you look at putting statistics, at 5' feet and longer, no one is at 100 %, yet the expectation seems to be that these fellows should make all of those putts.
I thought his club selection off of # 18 indicated that the was playing not to lose rather than trying to win.
I could be wrong on that, but that was my thought when he didn't use a driver.
One mustn't forget that missing a putt is not always caused by a poor stroke.
Many times a misread, misjudging of pace or misalignment is the culprit.
I've always advocated banning the long putter, however, while it's legal, I switched in May, and the result is that I know longer "yip" 1, 2 and 3 footers. The trade off is that I'm still trying to learn how to putt accurately from off the green, which iwas always good at.