Arsenal defender Myles Lewis-Skelly needs to understand "the line is really thin" if he is to avoid his career being derailed by disciplinary issues, according to head coach Mikel Arteta.
The 18-year-old had to be substituted in the first half of Tuesday's 7-1 mauling of PSV after picking up a yellow card in the 24th minute then shortly afterwards going in hard and late on defender Richard Ledezma.
