Career mode was one of the modes that received sweeping changes and additions across the board in FC 26. One of the striking additions was Deeper Simulations, which adds more behind-the-scenes action to crank up your manager realism.
Here's everything you need to know about Deeper Simulations and how it impacts the gameplay in FC 26.
Deeper Simulation in FC 26, Explained

When enabled, Deeper Simulation will let you pick five additional leagues that'll simulate with the main ones in FC 26. For example, if you choose to be a gaffer for an English club, you can have Italian, Spanish, and other leagues running in the background. You can either simulate all top-flight football or focus on more emerging competitions.
An option to enable it will be there at the start of a new career in the Quick Settings section. It is mentioned that turning it on will have a significant impact on performance, but there is no widespread issue as of now that sees performance dips, at least not on capable hardware.
With Deeper Simulation, Manager Careers also adds new historical data from the past season. You'll see top scorers, average ratings, cards, and other stats from the previous season. For the first-ever season, it'll use stats from the real-life football 24-25 season.
All that gives you more data to scout and helps you identify high-potential prospects. You can either check their general contribution to identify consistent performers or bet on young players who have improved from previous seasons.
Having multiple leagues will make you feel more "lived in" and make your manager journey even more immersive. It also gives you better scouting potential outside of your main league.
That's everything you need to know about Deeper Simulation in FC 26. Keep in mind that these are early days, and EA may tweak things here and there.
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