- get a good assistant manager with high stats in motivation, man management and player judgement. WIth those stats good I find they tend to give decent advise on how to handle the team talks.
-hold backroom meetings, and trust your advisors on who to praise or scold.
- turn on "player motivation" in the match window to get an idea of how your players and use that to tailor your team talk
anyway, those are some ideas, but I never managed a top tier team before, so you might just give it some time before your players trust you.
I mean, let's face it, if you were one of the top footballers in the world, and out of nowhere some guy no one even heard of before becomes manager of your team, you might not really be motivated by him right wawy, now would you....?