The Nigeria worldwide made his senior team debut at the Emirates Stadium under former manager Arsene Wenger in 2015, after joining the Gunners at age nine.
Iwobi who was put-on in the 63rd minute, was calm as he scored the final penalty in the International Champions Cup, ICC match that saw Arsenal beat Chelsea 6-5 on penalties after a 1-1 draw at the end of normal playing time.
He is one of the products of the club's academy and has enjoyed some level of success with the north London club.
Thibaut Courtois Goes AWOL In Order To Force Real Madrid Move
The Portuguese manager was said to have wanted to rejoin with his former player as he wished to strengthen United's right-wing. Hinting he would be willing to sell Courtois if he confirms he wants to leave, Sarri said: "I have no reaction on the agent".
Since then, Iwobi has gone on to play 98 games for the Gunners with nine goals to his credit.
Arsenal manager Unai Emery has described Alex Iwobi as a "great example" of how to rise through a club's academy to the main team.
Iwobi is the latest of Arsenal's younger players to commit their long-term futures to the club, following the likes of Hector Bellerin, Calum Chambers, Rob Holding and teenage midfielder Emile Smith Rowe. "Thank You", he tweeted. "Excited For 18/19 ❤️ #Gunners", the young promising Nigerian said.