Ryan was quite harshly adjudged by Bruce as not being good enough defensivley to play at right back, although his performences there under Jewell were impressive. Also the fact they have Melchiot there has something to do with it. Similaly, Valencia's place on the right wing is cast in stone so, given the lack of competition for a left sided midfield role (Koumas, Kilbane) that was where he ended up.
Newcastle, however, are quite strong in wide midfield positions; Duff, Jonas etc. It's a different story at the back though, Jose Enrique is a terrible player and Geremi is too old. Steven Taylor ended up at right back in the derby at the weekend, so it looks like being a slot (Ryan) Taylor could make his own.