not exactly a "rivalry"... More like a predictable one sided beatdown.
How is 10-23 a rivalry?
It is a rivalry because, even though Nadal won most matches, many of them were extremely tough. Look at Miami 2005, Rome 2006, WO 2007 and 2008, AO 2009, WTF 2010, RG 2011. Even matches like MC 2006, WO 2006, MC 2008, RG 2005-07 (especially 2007, where break-point conversión was the key) or Cincinnati 2013 were far from one-sided matches. Then, of course (and especially now that Federer is 32) there were many matches which were not so contested: even though the majority were Nadal`s, some of them were won by Federer, who, unlike Nadal, bagelled his opponent on all surfaces. A rivalry is much more than head-to-head...