View Nolan Ryan's career:
http://www.baseball-reference.com/r/ryanno01.shtml
As someone who watched Nolan Ryan's career from its inception, and a lot growing up as a Dodgers and Angels fan, Nolan Ryan was exactly what Syd Thrift says UNTIL he began to morph from a thrower into a pitcher. Check out the drop in walks that starts to happen around 1979 and then really asserts itself when he moves to Houston. During that same time he stops having seasons with 16+ losses that offset his wins.
Charlie Hough points out this shift. During his California career he would frequently beat himself with walks, averaging more than a walk very two innings. In the 1980s Nolan Ryan was a terriffic pitcher for a mediocre Houston team.
And I don't see how someone who was able to pitch at the level he did for a length of time very rarely seen can be classified as "above average." I don't think you can dismiss the longevity achievments of Nolan Ryan so easily. He had some of the best mechanics I have ever seen, interestingly enough, similar to Tom Seaver in that regard.
I can see where Syd is coming from if you only focus on Ryans career up to 1979. But you can't ignore 25 years of production. In fact, that's another huge plus for Ryan, because starting in 1972 he reeled off 20 consecutive years with 28+ starts (not counting the strike year of 1981). And in all those years he only dipped below 100 in ERA+ four times. Two of those were 98, one 94, and his worst ERA plus was a one-time mark of 91. Meanwhile he also posted ERA+'s of 194, 142, 141, 138, 128, and 124 (twice). And five more season of 110 or better.
So this kind of sustained excellence makes one a rather unique pitcher and one which is worthy of far more respect than "above average." If this guys is "above average," show me your comps that can match these sort of achievments.