You can definitley be good at MMA without having a wrestling background. If you train for an MMA fight, you will work on a few things like your ground game, striking, clinch, conditiong, and takedowns. Your ground game would most likley incoorperate a lot of jiu jitsu. Even guys like Matt Hughes, fantastic wrestlers, evolve to using BJJ techniques in addition to their superior wrestling. Along with the multiple forms of Martial Arts that you train in, you will come across your takedowns. Most takedowns will stem from Judo or from Wrestling. Most any gym that trains for MMA fights will definitley teach you takedowns (derived from wrestling). So I guess the point of this paragraph is that you don't need to be a wrestler but it could help. Even if you don't wrestle, you can definitly find people at your gym who have to help you work on the parts of wrestling nesscesary to MMA.