Aviles, 30, is not really the best example of an impact talent. He's had decent numbers in 2008 and 2010 for the Royals, but has interspersed those periods of usefulness with a couple of terrible years, hitting just .222/.261/.395 in 202 plate appearances this year. Interestingly, Aviles' effectiveness seems to be tied heavily to BABIP, with .223 and .231 marks in his off years, and .331 and .360 figures when he's been successful. The question is if either is the real Aviles, or if he's somewhere in-between.
It's understandable why the Sox would take a gamble on Aviles-if he turns out to be the 2008 and 2010 player, he's a solid middle-infielder who could potentially even replace Marco Scutaro next year. If he's the 2009 and 2011 Mike Aviles, however, he's not worth much at all.
Really, it's confusing why the Red Sox would give up a player like Yamaico Navarro in return. He's shown flashes of brilliance in the minor leagues at times, though he's looked overmatched at times in his initial exposure to Major League pitching. Kendal Volz, too, has shown potential given his at-times absurd peripherals.
The Red Sox could come out on top of this if neither Navarro or Volz prove to be capable of cutting it in the Major Leagues, but it seems just as likely that they've given up as much Major League talent as they've received, and have the greater possibility of really regretting the deal down the line.