Thiago Silva FIFA 21 can be unlocked by completing Squad Building Challenges. The Ones to Watch are a series of limited cards that automatically update based on the player's performance in the season. Here's how to complete the SBC to unlock OTW Thiago Silva.
Thiago Silva FIFA 21: How to Complete the Ones to Watch SBC
The challenge isn't too difficult, but you might need to fork over some coins to complete it.
You'll need to construct a squad with at least one Premier League player and a minimum Squad Rating of 82. The Squad's Team Chemistry must be at least 80. You'll have until Oct. 16 to submit the SBC.
Depending on the players you have, this challenge will run you at least 15,000 coins.
Squad Building Challenges are meant to get rid of cards you have sitting around, as squads you submit will be exchanged for the reward. You'll lose the cards in the squad, so be sure you only forfeit cards you don't use.
To make the most of the challenge, use the companion app or an external squad builder to find the cheapest solution to the challenge.