Yeah, similar to mlitney, promoting on popular forums like RealGM or OperationSports seems a smart way to go about it. Any way to advertise to people who are already into things like OOTP or Football Manager is def a great idea.
It helps if there are "ambassadors" who already have well-established outreach or followings on other platforms. Like if there's anyone who plays this game who already has massive reach on Twitter or Instagram or OperationSports, etc. them just saying "Hey guys check out this game" would be huge.