Yes, I read David Nalbandian retired this year due to an ongoing shoulder injury. He must be one of the best players never to win a slam; he was probably closest to winning the 2003 US open, as he held a match point v Andy Roddick in their semi, and I think had he won that match he old have beaten an exhausted Ferrero in the final. I know he got to the 2002 Wimbledon final, but he was well beaten by Hewitt. I think the highlight of his career was his 5 set win over Federer in the ATP Masters Cup, played on his best surface and conditions: indoor hard court.
However, I don't think he had the serve, movement, fitness or temperament to challenge Federer, Nadal and Djokovic on a consistent basis, which is why he never reached another slam final after 2002 and never got to no.1; but still a very talented player.
These end of year exhibitions really line the players' pockets though. I read Federer made US $12m from his South American exhibitions he played in December last year. I suspect that this had a lot to do with his unsuccessful 2013; as he did not do his usual December training block. Hopefully he does not play any meaningless exhibitions this year and does the requisite training block to prepare him properly for 2014.