How do you upgrade Madden Coach?

I think it requires only 1 Madden card to upgrade 1 level.

You can obtain 6 Madden Coach cards:

1 coach card for free today 1 coach card via the -M-A-DD-E-N set 3 coach cards via the 119 ovr sets 1 coach card via completing 6 of 7 achievements

I believe this is how the Madden Coach card is leveled up:

Level 1 = 1 card total level 2, an additional card = 2 cards total level 3, an additional card = 3 cards total level 4, an additional card = 4 cards total level 5, an additional 2 cards = 6 cards total

completing the master sets

Elite Coach Pieces don't go into John Madden so you can't upgrade him that way and you can only complete his 'M-A-D-D-E-N' set once.