Hattrick Man Marking Calculator made by Shadows RFC (666151). I made this for 1.5 hours, so any mistakes can be expected, although no one in the forum has found any error yet. Updated: 11 Dec 2017.
Updated on 07 Mar 2018 to reflect the latest changes: see forum post (17167129.23)
Defending* of your player:
Highest skill* of the marked player:
Your player is Powerful
Your player is specless
Marked player is Technical
Marked player is Unpredictable
penalty = 10 ^ 3.5 / (10 ^ 3.5 + 10 ^ 3.5) = 50%
Marked player performance (highest skill): 5
*That is not the real Defending skill and Highest skill, but the defending skill and the highest skill taking into account form, stamina, loyalty, Xp and health. (Thanks to LA-alpacstily for pointing this out)