Abreu is batting .266/.306/.418 in 2013 for the Giants, actually providing them with some decent offense over 85 plate appearances.
If the Giants were to buy, this could open up a spot for them to acquire an infielder at the trade deadline. All signs seem to point towards the team selling, however, which means that any deal to replace Abreu is unlikely.
Abreu has been a journeyman infielder for most of his career, playing for the Dodgers, Diamondbacks and Royals before coming to the Giants. His value stems from the fact that he can play multiple infield spots, which offsets his poor hitting ability.