"It is better to be on the pitch than on the bench, but the boys when they are playing did well, so if I'm on the pitch for 15 or 20 minutes, I do my best", he told BT Sport.
"But I think that, at this moment, he's not able to play for 90 minutes, so I thought it was better to give him 25-30 minutes when the intensity of the match has come down".
Emery added: "It is clear the result is not good for us but the process is continuing".More news: Donald Trump asks SEC to look into practicality of corp
"No, not in this moment", he said when asked if his side were among the favourites.
Chelsea are gearing up to face Arsenal at Stamford Bridge in a Premier League clash on Saturday. "So I think we have to work and we need to improve".
"In the second half we did very well also mentally".More news: Lost contact found in woman's eyelid 28 years later
On the touch-line, Sarri, wearing a baggy blue T-shirt and track-suit pants, waved his arms in frustration as he implored his players to close Arsenal down in their own half as the Gunners showed signs of fighting their way into the game.
Morata raced onto a long ball over the top and turned inside Shkodran Mustafi before firing home his first goal of the season.
Arsenal then missed another sitter, this time when Mkhitaryan blazed over after being set up by Iwobi.
Both sides tightened up after the break, but Sarri had the trump card when he introduced Hazard in the final quarter for a match-winning cameo. In the ninth minute Pedro finished off slick move started by Jorginho to put Gunners to the sword early.More news: Study finds moderate carbohydrate diets may be ideal for long-term health