Spurs had previously boasted the joint-best defensive record in the Premier League, only conceding six goals in the opening 11 games of the season, but were abashed by Manuel Pellegrini’s men.
And Holtby, who moved to White Hart Lane from Schalke in January, has made a promise that none of his team’s embarrassing performance will ever repeat itself again.
“It is still hard to take,” the Germany international wrote on his Facebook page.
“I definitely couldn’t sleep yesterday; it was probably the worst defeat in my life. Sorry to all of you Lilywhites.
“We have to show character now and bounce back from it! It isn’t over until it’s over.”
Tottenham have collected just one point from three Premier League matches in November without finding the net.