Hi again guys!
I've just played the match and i got a 0-1 win. Not very brilliant score, i know, but it allows me to jump to #1 as i've beaten the leader.
About the formations: actually during the day, my rival changed his formation from a 4-3N-1-2 (i didn't know whether to use 4-1-4-1 or 4-5-1 V style, and that was causing me headaches) to a 5-2-1-2 X style. He switched a 4* MC for a 3* DC.
By doing so, i assumed he was trying to play defensively (a tie would leave him still alone on top), so in minute 4 before starting the game, i changed my formation to a 3N-1-4-2. And it worked:

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Orders: both flanks as he had no players there, mixed passing, own pitch, no offside, no counter. I started with defensive mentality, scored minute 7, and switched to regular mentality from minute 20, just to see if i could see if i could get a bit more punch. But things didn't really changed, and as my team was performing quite well, i played with regular mentality till the end of the match.
Nevertheless, i must improve because my rival didn't attend the match, and i had the support of a friend so i got extra possession. Maybe that was the small difference that made me win, as the game was actually quite balanced.
Anyway, thank you all for your help and good luck!