The Gunners were leading 1-0 thanks to Pierre-Emerick Aubameyang’s first-half goal, with Nketiah introduced midway through the second period.
However, the former Leeds United loanee had only been on the pitch for less than five minutes when he challenged James Justin in the middle of the park.
At first, a free-kick was awarded to the visitors and the forward was shown a yellow card, but after a VAR review, which included referee Chris Kavanagh checking the pitchside monitor, the decision was reversed and a red card was shown.
Replays showed the youngster did catch Justin on the knee with a raised foot and it appeared the tackle was deemed as serious foul play by the officials.
The decision has caused plenty of debate on Twitter and both Lineker and Fabregas thought a red card was harsh.
The Match of the Day presenter wrote: “I understand why they’ve given a red, but not for me. Nothing challenge and I’m biased.”
While Fabregas wrote: “It’s a bad tackle but he doesn’t mean it at all. So unlucky if he gets the red.”
Speaking on commentary, former Gunners forward Alan Smith said: “Sometimes you think the players should be given the benefit.
“But James Justin, hurting, might not feel that. Chris Kavanagh looked at it twice and that was enough for him.”