Madden NFL 21 puts equal focus on attack and defence, and for the latter, you'll want to ensure you're cutting out passes.
A good interception can turn a match on its head, so you'll want to get practising.
Madden NFL 21: How To Intercept
Interceptions are a mix of defensive skill and timing and are easier based on the opponent throwing the pass.
Many of your players will be able to intercept a rookie's pass, for example, but more skilled QBs will take more than a simple catch to snuff out their attacks.
Players will automatically attempt to catch in many situations where there's less offensive pressure, but you can also press Y on Xbox, Triangle on PS4 or R on PC to try and pluck it out of the air with an AI teammate (if they have the skill for it).
If you prefer to take matters into your own hands, you can also press B to select the player closest to the receiver to allow you to make up ground and reach for the ball yourself.
Time it right, and you may be able to kick off a drive of your own.