Counter-Attacks There are 2 kinds of counter attacks (CA). The most common is the normal CA. The more rare kind is the random CA or special CA as it's also been called.
Normal CA To get normal CAs you need to choose to play the tactic. In addition it only works if you don't win the midfield.
There is a penalty to using CA. It reduces your midfield rating by 7%. Calculated in possession this means about 1,8% if you were close to winning the midfield, less if you have a much weaker midfield than your opponent. If you only would get around 10% possession playing normal, you only lose about 0,5% playing CA. If you win the midfield playing CA the loss in possession increases, but you don't get any normal CAs, just the penalty.
Which midfield rating counts? Before calculating midfield penalties from CA and PIC or after? Nobody knows for sure, but statistical data indicate that the midfield need to be weaker before calculating the penalties in order for normal CA to work.
What about MOTS and CA? Can you have a weaker midfield without MOTS and win midfield with MOTS and still have a working CA? The statistical data is very limited in this area as very few MOTS and CA at the same time. Until otherwise proved, it would be prudent to expect it not to work and that CA requires a team to lose midfield both before and after penalties and bonuses.
How many CA's can you get in a single match? As with so many other things this is a secret HT keeps to themselves. Before random CAs were implemented 3 CAs was the highest recorded number and that was a fairly frequent number. It was then believed that 3 was a maximum number. After random CAs were implemented a few matches with 4 CAs have been recorded. It seems likely that they are caused by the team getting both normal and random CAs, but there's so far no way of knowing for sure.
Random CA Unlike the normal CA you don't need to play CA tactic to get a random CA, and you can also get it when you win midfield. They are much less frequent than normal CAs, but if you have a relatively strong defense they do appear from time to time. They can of course also appear even if you play CA tactic, but there is no way yet of telling which kind you get. Not that it really matters either.
How many random CAs can you get in a match. The highest known number so far is 3. That's a very high number in a single match for a type of chance that's rare to start with, so don't expect to see it happen to you. So far it's only 2 known matches where it's occured.
General No CAs, normal or random, are special events (SE). They are continued regular attacks. That means in order to get a CA, you first have to stop an attack. That requires you to have a relatively strong defense compared to your opponents attack (or a lot of luck). Any stopped attack can be converted to a CA. We know for sure that your CA skill have a major impact on your ability to convert a stopped attack to a CA. Other factors that may play a part are by how much the attack missed and how many CAs you've already had in that match.
A formula may look someting like:
Chance of converting = K + (CA skill * F) + miss percentage -(X*P)
K = Fixed base percentage F = Multiplier percentage for CA skill X = Number of CAs already achieved in the match. P = Penalty percentage for previous CAs in the match
CA skill CA skill is calculated from the skills of all playing defenders and defenders only. A base number is calculated from adding the values of their defending skills and their passing skills. Passing skills are multiplied by 2. This base number is modified by the players form and experience and the result is a CA skill which appears to be completely linear.