Arteta was impressed by Lacazette's focus and determination despite being omitted from the starting XI.
Mikel Arteta was pleased with Alexandre Lacazette's attitude after the Frenchman came off the bench to score in Arsenal's narrow win against West Ham on Saturday.
Lacazette, who replaced Eddie Nketiah in the second half, scored the only goal of the game at the Emirates as the Gunners secured all three points to move five points behind fourth-placed Chelsea.
The 28-year-old has now scored nine times in 26 league matches this season.
After the match, the Arsenal boss said starting Lacazette from the bench was a tactical decision.
"I have two strikers at the moment that are making life difficult for me, but at the same time it's very good," Arteta told reporters.
"They are both scoring, they are both in a good moment. I decided to play Eddie today for the type of defenders they had and the game plan we had, but knowing that we needed Laca [Lacazette] in the final moments.
"He was ready to do that. I saw it straight away the moment I was talking with him, giving him instructions on the touchline.
"He was alert, focused and I could see in his face he was really determined to come out there and score the goal like he did."