Rafa Benitez has explained his decision to take off Yoshinori Muto.
There were boos at St James's Park when Benitez replaced Muto with Joselu on Saturday.
Brighton and Hove Albion – who faced 27 shots – held on to win 1-0.
READ MORE: Blow as Newcastle lose key man
The result left Newcastle United propping up the Premier League ahead of Saturday's game against Southampton at the St Mary's Stadium.
Benitez felt that Joselu would unsettle Lewis Dunk and Shane Duffy, who were outstanding in the heart of Chris Hughton's defence.
"I thought if we put Joselu there he would try to compete with them, because we were so much in control," said United's manager.
"It was another different approach with crosses from the wide areas.
"The last minutes we were giving the ball away from the middle two or three times. We have to be more composed on the ball and then try to do the right things in the wide areas to create something more.
"Through the middle they had too many bodies and it was difficult."
Hughton paid tribute to Dunk, one-time Newcastle target, and Duffy after the game.
Brighton's manager said: "You know with these two, if it's a game in which there are going to be a lot of crosses coming in, they're the type that are very happy getting their head on the end of it, and also throwing their bodies into the line of the ball."
Meanwhile, Benitez has been without Salomon Rondon for the past month.
The on-loan striker – who has been sidelined with a thigh injury since last month's goalless draw against Crystal Palace – is pushing to return for the Southampton game.
"He's getting better, but he has been away for a while," said Benitez. "I don't think we expect just one player to make a big difference.
"If you have Rondon you have more competition up front. Maybe he can help. We need the rest of the team to do their best every game."
Rondon has scored one Carabao Cup goal for United since joining from West Bromwich Albion on a season-long loan from relegated West Bromwich Albion.