UFC 66 - WIN Marrero (Preliminary Card)
UFC 70 - WIN Cro Cop (Main Event)
UFC 74 - LOSS Couture (Main Event)
UFC 80 - LOSS Werdum (Main Card)
UFC 86 - WIN McCully (Preliminary Card)
UFC 91 - WIN Hendricks (Main Card)
UFC 96 - LOSS Carwin (Main Card)
UFC 102 - Tuchscherer (Preliminary Card)
The first time you fall off the main card is not a huge deal. As long as you were previously a name, you're not in danger of being cut.
The second time you fall to the preliminary card, you're in trouble.
Notice the talent difference between his first trip to the prelims and his second. Chris Tuchscherer is the guy who tried out for TUF 10 and they thought he was too good, so they signed him to a contract instead.
This is a whole different ballgame than fighting McCully/Hendricks. The UFC hoped for Gabriel Gonzaga to get back on track by placing him in those fights.
It's like when you're at a bar talking to a pretty girl. Unless you've found the Holy Grail of bars, the ratio of pretty girls to guys is always working against you (kind of like the ratio of championship belts to fighters). You need to capitalize on the conversation or else you might not get another opportunity.
Gonzaga stumbled over his words, the pretty girl is talking to someone else now, and he's stuck with a fat chick who thinks too highly of her boobs.
Good luck, Gabe. You're gonna need it.