Mikel Arteta was unable to give a diagnosis on Bukayo Saka who came off with a thigh issue at Bramall Lane.
The versatile 19-year-old hobbled off in Arsenal's 3-0 win at Sheffield United.
Saka went down in the second-half with what looked to be a muscle injury as he collapsed to the ground with no one around him.
He commented that he felt an issue in his thigh whilst Arteta also revealed that Gabriel Martinelli had to battle through an ankle issue ahead of Thursday's Europa League quarter-final
He told BT Sport: "I am really happy with the way we played, we scored some really nice goals and controlled the game the way we wanted. We played at a high level. From the start I felt the boys were at it, we were efficient.
"We had good distances to play with each other and they understood the space.
"It's the first time Granit Xhaka has started at left-back, it's a possibility for him. He has the qualities to play there.
"Bukayo Saka, the last thing we need is another injury but he felt something in his thigh.
"Gabriel Martinelli twisted his ankle but he's a tough boy. Against Prague Lacazette missed two big chances and he needed those goals. He has been playing well.
"This is ideal preparation for Thursday. It has been a long run without a clean sheet."
Arteta was already without a quartet of players and his injury woes could be set to worsen.
Kieran Tierney will be missing for several weeks while Martin Odegaard had been suffering with an issue he picked up during the recent international break.
Pierre-Emerick Aubameyang and Emile Smith Rowe were both late casualties.
The former was ruled out with the flu while the young playmaker had an ankle problem.
