Seriously, if you've never played it, you need to track down a copy of this game. It's a mix of japanese and english but it's worth wading through to play. The Career Mode is called Boxer's Road.
You have to set your schedule like this.
You actually have to make weight for your weigh-ins and if you don't, you get penalized.
More on the schedule
There are multiple boxing federations with their own belts, like 12 in each division. You can move up and down in weight. You get ranked in different federations. I started at featherweight in my career and moved up to welterweight. My guy was fukking Amir Khan to a tee. At the lower weights, my speed and punching overwhelmed people, when I moved up to 147, I learned that my chin was some fukking Grade A China.
Watch this and look at how a small japanese company absolutely shytted on EA and their offerings in Career Mode. This is better than MLB's Road to the Show, NBA2K's My Career Mode and Fifa's My Player Career Mode. fukk, I am due for my new playthrough anyways here on the emulator. If someone wants to give it a whirl, I keep the ISO on deck on the PC at home.