It’s always a giant risk for any player to dive in for a challenge when they are on a booking, and Hector Bellerin might be lucky that he wasn’t sent off here.
It’s not a particularly malicious challenge, but he’s very late and it does have the look of a textbook yellow:
Pictures from The Premier League
You can see from Justin’s reaction that he cannot believe the decision, but it’s also hard to tell if there was actually any contact here.