It was suggested Newcastle players could've been distracted as City won 4-0 on Saturday.
Howe said: "If that is the case, then we are in trouble.
"Our Premier League season will be over really by the time that game comes around. It can't be the focus. It is on the horizon it should be a positive not a negative distraction. I would encourage the players to look at it that way, we have to go back to work, the work is the Premier League the day in and day out stuff.
"We have to perform better. That is three of our last four performances in the Premier League that haven't been good enough. They have all had similar traits in them (Forest, Bournemouth and Man City), so back to basics for us.."
He continued: "We try to address it internally. I don't know, people will naturally assume that the cup final is a negative distraction and it was not a great performance from us today. I need time before sticking my colours to the mast on what went on today.
"It was a tough game, they are still the toughest team to play against. We were not at our best today.
"Goals change games, and the goal we concede early was a tough one for us. All the goals we conceded today we will look back on with frustration. It becomes difficult when you chase the game today, really tough.
"They ask so many questions of you, put you under pressure. They did not have a bundle of chances but they did what they needed to do. It's about growing for the next games and learning from today. When you come back into these arenas, fare better, that's the challenge."