You're right, but that said, some of the most successful coaches internationally of modern teams had very little playing background at the highest level. Best example I know of is Jose Mourinho - won the Champions League at Porto and Inter, won the Premier League (and the FA Cup IIRC) at Chelsea, now has won the Copa del Rey at Real Madrid and is going to give the CL this year a massive crack IMO. This is a man who started coaching in his early 20s and has gone through the systems all the way to the top. Andre Villas-Boas (Chelsea manager, won Europa League with Porto last season) is similar in terms of path.
There are probably plenty more examples, especially in the US where it's much more meritocratic than in the European systems.