Trades involving young, cost-controlled, starting-quality middle infielders do not happen very often. Shortstop and second base are premium positions in the MLB and teams, unsurprisingly, tend to be unwilling to part with players who can competently play said positions.
Over the last few years, there have been a fair number of trades involving fringe starters -- guys like Tommy La Stella, Darwin Barney, Didi Gregorious -- but rarely bona fide starters. Not necessarily superstars. Just guys you know will be able to hold down the position.
Jean Segura is one of those guys who seems pretty certain to be a quality player at shortstop for a while.