Mauro Diaz is gone, missing from training, and FC Dallas could be about to lose arguably its best player over the past five years.Probably.Diaz, second in Major League Soccer with eight assists, was missing from training Wednesday after being dropped from the 18-man FC Dallas squad for the past two games.When asked today to confirm a potential Diaz sale, FC Dallas technical director Fernando Clavijo couldn't confirm a completed transfer but did acknowledge a sale was on the table."Yes, correct.