On a day of surprises in the Barclays Premier League, the Baggies produced a performance that belied their lowly standing to deservedly win 1-0 at White Hart Lane.
Previously winless West Brom had begun the day bottom of the table, although it was Tottenham that looked like the relegation candidates on Sunday.
Spurs were awful from the outset across the field, managing just one shot on target and looking unstable at the back throughout.
It was not the way Kaboul wanted his first match as the club's official captain to go and a performance he was at a loss to explain.
"We're all disappointed, of course, after this poor defeat," he said.
"I think we played with a slow tempo all of the game and we never looked dangerous, a threat for West Brom.
"They took their chances and they scored from a corner
It was not good enough from us.
"I am still questioning everything, what went wrong
We didn't create any chances.
"We were just inviting them to try to score
It was not good enough from us.
"But that's football and we have to go back to training with a better mentality also."
The defeat stretched Spurs' winless streak to four matches in all competitions - hardly the ideal preparation for a crunch week.
Nottingham Forest arrive at White Hart Lane as Mauricio Pochettino's men get their Capital One Cup campaign under way on Wednesday, before they make the short trip to bitter rivals Arsenal for the north London derby at the weekend.
"It is a tough week," Kaboul told Spurs TV
"Every game is tough.
"The game on Wednesday is important for us because we want to win something this season
"Forest are a good side, they are doing well in the Championship and we have to bounce back straight away on Wednesday."
West Brom are also in Capital One Cup action on Wednesday, when they will look to build some momentum against Hull at the Hawthorns.
Their penalty win over Oxford in the second round was their only previous success under manager Alan Irvine, who admitted a mixture of relief and pride after winning at White Hart Lane.
James Morrison scored the decisive goal against Spurs, although the undoubted star of the show was England international Joleon Lescott.
Having joined on a two-year deal in the summer, the 32-year-old produced an outstanding competitive debut and came close to capping a wonderful defensive display with a goal.
"We would have taken a big risk had we put him in when he was not ready," Irvine said of Lescott.
"We already had one setback against Nottingham Forest (when Lescott came on at half-time but later had to be substituted)
I keep trying to explain that we want to put people in the team but they have to be ready
I felt he was ready.
"He had two weeks of training and he had that without feeling any twinges
We felt this was the right opportunity to put him in and he played very well."
Source : PA
Source: PA