Preface: Rosterbation is extremely boring and utterly pointless. We have no idea about player availability and what the potential trading partner is demanding in return. Therefore, I am not going to propose any specifics.
Emmanuel is having an awful year. A really awful year. A Neifi Perez says "hello" kind of year. If he doesn't change his current rate stats he will be worth -2 wins below replacement over the entire season (or -1.2 over the remaining games). Now the good news: Since Burriss sucks more than a Heidi Fleiss escort (yay for dated pop-culture references!), replacing him with an average player results in a huge swing for the Giants.
Here is a list of 2nd baseman who are in +/- .3 wins of essentially a league average player right now (from best to worst).
Acquiring any one of these players would essentially add 2 wins to the Giants season total. That's huge! For perspective, if the Giants were to trade the entire farm system to Milwaukee for Ryan Braun (1 of the 3 most valuable outfielders so far this season) and then insert Braun into the lineup in place of Fred Lewis, the Giants would gain.... 2.5 wins. The Giants can do the equivalent of adding a star to the roster just by trading for a decent 2nd baseman. If they are serious about competing in the NL this year, Sabean HAS to do this. There is probably no cheaper (realistic) trade in all of baseball that can have more influence on a single team's season than the potential replace-Burris trade.