Torreira made his Premier League debut on 12 August, coming on as a substitute on the 70th minute in a 2–0 defeat to Manchester City. Torreira registered his first assist of the season, by setting up Alexandre Lacazette's winning goal in a 3–2 win over Cardiff City. Torreira made his full-debut and his Europa League debut for Arsenal in the 4–2 win over FC Vorskla Poltava on 2 September, before being replaced in the 57th minute by Mattéo Guendouzi. Torreira's performance in Arsenal's 1–1 draw with Liverpool drew particularly high praise from fans and pundits alike, picking up the man-of-the-match award. On 2 December, Torreira scored his first Arsenal goal and picked up another man-of-the-match award against Tottenham Hotspur when he latched on to a pass from Pierre-Emerick Aubameyang to slot the ball past Hugo Lloris to give Arsenal a fourth goal in a 4–2 North London derby victory. A week later, on 8 December, Torreira scored a late 83rd-minute winner against Huddersfield Town with a bicycle kick, giving him his second goal in as many games at the Emirates Stadium. In the match, Torreira was also awarded his fifth consecutive Arsenal Man of the Match performance.