The Defence is the one, trying to tackle the opponents offensive players. So first of all you need for your defensive line good tackling skills.
Physicals are always a good thing to have, your defensive ends schould have high speed and agility to put pressure on the quarterback.

Your offensive line does the exact opposite - they try to block the defenders and make space for the qb, rb oder the receivers. They need blocking as primary skill.
Secondaries are as well agility IMO and for both, OL and DL footwork. You should position your strongest OL-players at the 'offensive-tackle' position, to avoid pressure and sacks.

I'm not sure here about the tactical skills - vision and positioning.

McCatrice wrote: Please, I want to know what is the principal difference between OL and DL ?? Because they have the same caracteristics but they can't change their poste ( OL to DL or DL to OL . Sorry for my english.

Train them like this:

DT->Find physical caps (17+ str IMO)->Tackling to 7->Footwork/tacticals/agility to 7, probably in that order
DE->As above, except 17+ speed too, and agility swaped with footwork
OL->Find physical caps (17+ str)->Blocking to 7->Footwork to 7->Tacticals to 7->Possibly agility to 7 on OT

When thats done, you go to 10 and so forth.. That will ensure you a strong team for low wages (train all your players evenly in at least 2-3 primary skills)

McCatrice wrote: If I understand, I must train strengh ( at max ) , after tackling ( or blocking ), footwaok, tacticals ..... ??

Okay, I will add my order for each position, breaking down the lines by position:

OT-Max strength(18 min), spd(14 min), blocking, agility, footwork, then tacticals

OG-Max strength(18 min), spd(12 min), blocking, footwork, then tacticals

OC-Max strength(18 min), spd(any), blocking, footwork, then tacticals

DT-Max strength(18 min), spd(12 min), tackle, footwork, then tacticals

DE-Max strength(18 min), spd(18 min), tackle, agility, then tacticals

The admins have stated that every player uses anywhere from 3-5 skills (not counting physicals, the way i read it). Therefore, you can either pick the top 3-5 skills you think each position needs and work on them evenly or you can focus initially on primary and then slowly move up the secondary skills until you are satisfied with the performance and salary

thanks for your help, today my defence do a good game. I change my defenders positions and it's better