Ramon Ramirez is a little (5'11") guy with a weird career path. Born 8/31/1981, he was signed out of the Dominican Republic by the Rangers as an outfielder in '96 and ended up starting his pitching career with the Hiroshima Carp in 2002. He's still only 23 and his strikeout numbers are pretty good, so we shall see. He does tend to allow home runs at a pretty good clip and therefore hasn't posted real impressive minor league ERA numbers. He has good numbers at Dayton so far this year (good K/BB, only 3 homers in 81 innings) but he's old for Single-A. He's spent most of his time starting this year but the experts say he's middle relief material in the bigs. Baseball America has him at #23 in the Yankees' system. John Sickels doesn't list him at all this year (or in '03 or '04).
Eduardo Sierra is taller (6'3") and younger (born 4/15/1982). He's a Dominican as well, originally in the Athletics' system until they flipped him to New York for Chris Hammond a year and a half ago. You can sum Sierra up in one word: walks. And lots of them. He's at 5.93 BB/9 this season with AA Trenton and was at 8.3 last year with Tampa. High walk rates and Coors Field go together like Shaq and Kobe. This guy hasn't started since low-A and was obviously not long for the Yankees, who can't bear to pay a middle reliever the minimum when they could possibly pay him $5 million. BA ranks him #16 in the New York system based solely it seems on the fact that he can throw mid-90's. Sickels, again, demurs.
I'm not excited about either of these guys, and you shouldn't be either. The only reason either of these fellows even appears in the prospect books is you have to put some names under "New York Yankees."