The 18-year-old will be making his Premier League debut at St James Park and Wenger revealed that the midfielder had been impressing in training ahead of the clash.
Willock is the fourth player born after Wengers first match in charge of Arsenal to make an appearance for the club – Ainsley Maitland-Niles, Reiss Nelson and Eddie Nketiah are the other youngsters on that list.
The Gunners have made six changes from their draw with CSKA Moscow on Thursday night and Pierre-Emerick Aubameyang and Alexandre Lacazette start up front together for the first time.
Asked about his decision to play Willock, Wenger replied: He does well in training but the real step is in the competition, Wenger said.
Its a good opportunity for him and a good chance for me to see whether hes ready to play regularly at this level.
— Arsenal FC (@Arsenal) April 15, 2018
A combination of tactics and injuries meant that Aubameyang had not started alongside Lacazette prior to Sunday afternoon but Wenger is confident that the duo can play in the same team.
Yes, I think they can play together, he said following Arsenals defeat of Stoke earlier this month.
Aubameyang has played a long part of his career on the left.
And when [Robert] Lewandowski was at Dortmund he was on the left.