After Sergio Perez was sent off as expected, his successor was named later today. It's Liam Lawson. Christian Horner revealed what decided in his favor over Yuki Tsunoda.
The difference was very minimal, the decision was very close, Lawson was finally chosen because of his better race pace:
“It was a close call because Yuki is a very fast driver. He already has a lot of experience; he excelled in the tire test in Abu Dhabi, and the engineers still praise him today for what they saw there. But when we compared his data with Liam's, we saw that his data was better than Tsunoda's, especially when it came to race pace. Their qualifying results are almost identical, but there's no denying that Lawson only has 11 races under his belt; he's sure to be much better and stronger over time.”

"He is mentally strong, with great resilience, but the most important thing will be not to put too much pressure on him. He will have to face the best driver of his generation, but he would be better off completely ignoring what is happening with Max Verstappen and focusing only on his own task and development. If he does that, he will be fine!" - said Christian Horner.