I've been playing and really enjoying http://www.derbymanager.com/ for the past few months, and it's weird to see it's not more popular. It's a completely free - as in, there's literally nothing you could possibly spend money on - online football (soccer) manager with depth comparable to the early Championship Manager games. It's still changing a lot, as the dev is very active trying out different ideas, but it's very playable with good match engine and training system. There's one match a day and each season is played during a calendar month. You start off by taking over any (fictional) team in the bottom division and work your way up or hop around different leagues.
I'm not connected to the dev in any way, but there's a good if small community on Discord, and it's easily one of the best online managers I've played. It just needs more players as currently it's more of a solo experience with most social activity is going on in Discord. I've played for quite a few seasons now, so ask away if you have any questions about the game!