Jeremy Hermida is probably one of the better-hitting outfielders in the league; while Jeff Francoeur is a Gold Glove caliber outfielder, his offense has never been as good as it was in 2006.
Hermida is a better hitter than Francoeur and is a very good defender in right field.
The Marlins likely will compare Hermida's and Francoeur's offensive numbers and will likely decline the trade, being the latest team to decline Francoeur.
Hermida's numbers won't set records, but they're solid. This season Hermida is hitting .276, with eight home runs (10 homers away from last years total), and 29 RBI. He has 63 hits in 63 games.
Francoeur's bat is much worse than Hermida this year, hitting .250 with four home runs, 29 RBI, and 58 hits in 61 games.
As you can see, Hermida is a better hitter.
That's why I think the Marlins will reject this trade, just like the Phillies, Royals, Red Sox, and Mets before them.
Why would they want to get rid of one of their better players and make a division rival better while making themselves worse?