The Scottish midfielder netted the first of The Bees' three goals to get them back on level terms just before half time. He spoke to us pitchside after the final whistle.
"That was a very good win," said Ali. "Kev [O'Connor] challenged us before the game to keep the same high standard that we set against Rangers and I think we matched that if not bettered it today.
"We didn't get off to an ideal start obviously, but I think the boys reacted well. We finished the half strong and got the goal. We just grew in confidence from that and we started the second half really well. I thought we saw out the end of the game really well as well."
On the back of a 3-0 win against Rangers, a 3-1 victory over United caps two good results in quick succession. The 19-year-old agreed, he said: "They're two very good results. I think now it's just a case of keeping the run going and try to finish the season strong."
Ali's goal came at a crucial time for the team but also seemed to give him confidence in the second half, and he touched on the lessons learned by the squad as a whole.
"I missed a chance early on," he said. "I feel like I should have scored but I knew that the chances would come and it would just be a case of taking them next time and I'm glad I did. I think it was an important time to score.
"Man United are obviously regarded as a very big team, we've beaten Chelsea earlier in the season. We have them again next week, we need to go into that with confidence and hopefully get another win."
With the end of the season now in sight, following a trip to Portugal and two fixtures against Manchester City, Ali took us through his targets for the rest of the term.
"I think to get a consistent run in the team," he said. "To keep showing that I have got the quality to go all the way. I feel physically better now than I ever have, so I feel like I will finish the season strong."