The Reds staged a dramatic fightback to win 4-3 in Germany, a result rendered unlikely by the concession of three sloppy goals, giving Phelan and his fellow coaches food for thought with the season proper looming large.
"It was exciting, all right," Phelan told MUTV. "We made a game of it because we gave a couple of sloppy goals away, which we shouldn't be doing. But credit to the players; they came back, they showed a little bit of spirit at the end and it was a good victory.
"It's important we score goals. We can't go into a championship and be struggling finding the net. We have progressed in that department, but we have to look at it from the point of view of how disappointing it was to give the goals away in the first place. We switched off.
"We look a team that can go forward and score goals, but we also look as though we can concede as well, and that's not good."
With the six-game DHL Tour now at an end, Phelan declared himself happy with the state of the Reds' squad ahead of the 2012/13 Barclays Premier League season.
"It's been a long one, it's took us all over the place but that's part of being a Manchester United footballer," he conceded. "We've taken the team to numerous continents and we've come away relatively unscathed so we're happy with that.
"We now have to settle down a little bit and get focused now on the Premier League. That will be a big challenge."