They have amassed 33 goals between them in a perfect start of four Premier League wins but could not match that in the Champions League, salvaging 1-1 draws in Wednesday's openers.
United's point at their main Group C rivals Benfica was a better one than City's one at home to Napoli, the least fancied side in a strong Group A, but both had to come from behind to draw so know it could have been worse.
Champions League debutants City put their profligacy in front of goal down to over-excitement and coach Roberto Mancini said they would have no such trouble in their next game away to Bayern Munich later this month if they went back to basics.
"I think the second game will be more calm," he told a news conference after a 74th-minute free kick from Aleksandar Kolarov levelled the match. "Bayern Munich are a fantastic team but we have a team that can win very well.
"Did we show a bit of naivety? Yes, absolutely. But I'm happy with our performance. Every game in the Champions League is different and difficult, for us it's important to play simple football. If we do this we will play better football."
TOO CAUTIOUS
Inexperience was not a problem for former winners and last season's runners-up Manchester United whose equaliser in Portugal came courtesy of the Champions League's oldest goalscorer Ryan Giggs, who turns 38 in November.
"Our possession in the first half was too cautious in the first half," Sir Alex Ferguson told reporters. "It was the kind of possession that gives you a certain control but doesn't win you the game.
"I think a draw was a fair result."
The pair now return to league action and despite Mancini's assertion that "it is impossible for a striker to score three or four goals every game" the likes of Sergio Aguero and Edin Dzeko, who have scored six each this season, will try to do so.
City travel to Fulham on Sunday while Manchester United entertain title hopefuls Chelsea in what is their stiffest test so far this season.
Ferguson had even rested some players for that big Premier League game, leaving out winger Ashley Young and keeper David Dea for the Benfica match.
"David de Gea will play on Sunday. That was the understanding we had before the Benfica game and it doesn't change," the manager said.
"We gave Ashley Young a rest tonight as I felt he needed a little break after the two games he played for England and the one for us at Bolton. He is new to the club and obviously every game is massive for him here, so he'll be nice and fresh for Sunday."
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