Demonstrations by Newcastle fans "affected" the team during the 3-1 defeat by Tottenham, according to caretaker manager John Carver.
The Magpies suffered a sixth successive loss in front of a crowd of 47,427 - their lowest in the league this season - as fans protested against owner Mike Ashley outside St James' Park.
"It affected me and it affected some of the players," Carver said.
There are more protests planned for Saturday's home match against Swansea.
Supporters are being asked to stand in the 34th minute. representing the club's £34m bank balance that organisers believe should be spent on improving the team.
"I know there is another one coming this week, but at least people are coming in to the stadium," added Carver.
"If it's a protest for one minute and that it only lasts for one minute then we've got 89 minutes to get on with the game."
Fan-run website ashleyout.com organised last week's demonstrations, handing out 20,000 leaflets to supporters an hour before kick-off.
An ashleyout.com spokesperson said: "This is only the start of a long and sustained campaign to remove Mike Ashley."