Arsenal manager Mikel Arteta said he had to pick striker Eddie Nketiah against Nottingham Forest because of his attitude in training this week.
Nketiah scored his first goal since January as Arsenal started the Premier League season with a 2-1 home win.
The 24-year-old Englishman missed out on a place in the starting XI for the Community Shield triumph over Manchester City last weekend.
"I'm delighted for him because he is a role model," Arteta told TNT Sports.
"Nketiah was very disappointed he did not start against Manchester City, but he came on in the game and had a huge impact, trained like a beast this week, telling me 'I deserve to play'.