What’s the most winning tactics available?
First of all, tactics should be picked for each team individually. Identify weaknesses and strong points of your players. Stronger players are usually the fastest ones (that means their red-coloured «Speed» indicator is 75 or higher). If you have a slow defense line, you should play with 4 players in the defense. If your defense line is fast, play with 3 players in the defense and put one leftover player in the midfield or in the offense. If your offense is rather slow then focus on faster midfielders (they are the core of the team and the most important part of it). Don’t hold back your fastest players for replacement purposes, they belong to the main roster (with the exception for players with roughness indicator 15 or higher, they will do more harm than help). Fastest players should be placed in the middle of the field, on the lines in accordance with their roles. They’re much more effective in that position. Due to their speed they can reach flanks in time to support the attack of their own team or to stop the attack of the enemy.
Replacements should be thought through, with the players’ fatigue and the current situation on the field taken in consideration. For example, don’t try to make the defense line stronger if you’re losing and you need to play for win. Also don’t replace players who are not fatigued yet (usually it takes 60 minutes of the match to become fatigued). Don’t replace a tired but good player with a fresh but inexperienced one, replacements like this are pointless. In case of injury or player removal replace him with a forward and put him on the line, where the removed player was.