Kolasinac, a free transfer from Schalke, played as the left-side centre back in a makeshift defence for Arsenal's Premier League opener against Leicester.
Neville was quick to spot who he believed to be most at fault, with Kolasinac coming in for significant stick.
"I have to say, their new centre-back, it's so irresponsible what he does", Neville said speaking on Sky Sports.
"For us it was a bit disappointing with the goals that we've let in and we shouldn't really be conceding in that way, but I think we showed great determination and great togetherness to get back into the game and we won it towards the end of the game". "It's poor from him".
Sead Kolasinac may have become an instant fans' favourite on his debut against Chelsea and was part of Arsenal's winning team over Leicester on Friday night, but Gary Neville was less than impressed with what he saw.
The 24-year-old assisted Welbeck for his equaliser at the end of the first half, with the England worldwide opening his account for the season.