Man United took the lead in the 61st minute thanks to a penalty from Bruno Fernandes after Bournemouth defender Alex Jimenez pulled Matheus Cunha's shirt in the penalty area.
A few minutes later, Diallo was fouled by Adrien Truffert in the penalty area, but VAR said that collision was "not enough to constitute a foul".
Man United's calls for a penalty were ignored by the referee. A few seconds later, Bournemouth put the ball down to the opposite half and equalized thanks to Ryan Christie's goal.
Man United continued to take the lead in the 71st minute when James Hill of Bournemouth unintentionally scored an own goal after Fernandes' corner kick.
But the turning point came in the 78th minute when Maguire fouled striker Evanilson in the penalty area, leading to the Man United center-back receiving a red card and Bournemouth equalizing from a penalty.
While Bournemouth coach, Andoni Iraola, said that the collision with Diallo "was never a penalty", Carrick argued that the plays involving Cunha and Amad Diallo were completely the same.
We should have had another penalty. For me, both situations are the same. If you use both hands to pull someone in the penalty area and they fall while still controlling the ball, then in my opinion it is two penalties. However, Cunha's ball was penalized, and Amad's was not.
Anyway, the referee was wrong in one situation, but awarding a penalty in one situation without giving the other, I can't understand. I think that's crazy. It's really a bit difficult to understand.
After that, Bournemouth scored and then everything became chaotic. We should have had another penalty, but the match was completely different," Carrick said after the match.
Captain Bruno Fernandes also added: "We were penalized in a situation similar to Amad's case.
One situation is awarded a penalty, the other is not. I know referees can hardly award two penalties to the same team in the same match, but what I don't understand is why VAR doesn't intervene in that situation. Either one of the two is a penalty, or neither is a penalty.
Despite the draw, Man United is still ranked 3rd in the Premier League table with 55 points. According to Carrick, Man United is still in a favorable position in the race to win tickets to the UEFA Champions League next season.
We are in a favorable position and have achieved this position thanks to efforts, good results and impressive performances. Man United has made some progress. There are still things we can improve and become much better. I am satisfied with what has been achieved, but we are still not satisfied. Certainly, we want to achieve more success," Carrick emphasized.
After this match, Man United will have a break of more than 20 days before entering the next match against Leeds United at home.