thank you for the answer, Joe.
I guess now I understand the "traditional" TTC function : safeties, line and RBs.
But the thing I don't understand is how some great players (see the 2008 open run vid on the mfca.org videos section) play without TTC...I guess they use big rosters (40+ based figures teams) to insert options in the game, in place of using the ttc dials ?