u/FPLJoeYT

It's not easy to plan a chip strategy without knowing what the final booster is.

So, I found this...

>Clean Sheet Shield
Any goalkeeper, defender, or midfielder in your team will only lose their clean sheet after conceding 2 goals.

The Mystery Booster will be officially released on 24th June, ready for use from R32 (Matchday 4) onwards.

Note: This is not officially confirmed. While unlikely, it's not impossible that this is either stale code that wasn't removed, or even a red herring left by some devs who thought it would be a good laugh.

[Source: https://play.fifa.com/json/langs/fantasy/en.json]