William Saliba is officially property of Arsenal. The young defender will go on loan back to Saint-Étienne for another season before officially making the move to North London. Here are some basics about what Arsenal can expect from their shiny new center back. First, he’s very very young. At only 18 years old, it’s no surprise that Saliba doesn’t have very many minutes under his belt. Still, he only made 16 league appearances for his club last season, and only played a full 90 minutes on 11 occasions. His output when he did play is quite strong. There are, of course, considerable questions about what it means to be a center back who makes a lot of tackles and how that relates to broader team defense, and positional awareness, but Saliba definitely won the ball a lot, 2.5 possession adjusted tackles per 90 minutes, and has an all-around profile with very few statistical weaknesses. The challenge for Saliba will come when he eventually has to adjust to the different tactical questions that playing for Arsenal will pose, although it’s fair to wonder exactly how different his job will really be. Despite playing in vastly different contexts, top six in England and France but an above average defense in France, as opposed to a bottom half one in England, Arsenal and Saint-Étienne actually have fairly similar outputs. That said, the two teams have chosen to defend very different areas of the pitch. When Arsenal defend high up the pitch, they make their stand primarily in central areas. Saint-Étienne press very high and wide, but largely cede the center until the ball is close to their own penalty box. Arsenal are clear getting a very talented, very active center back. He can physical do it all, but that doesn’t mean that when he arrives a year from now, he’ll be ready and able to do it all for Arsenal.