Thomas Frank described Tottenham fans who booed Guglielmo Vicario during the 2-1 defeat to Fulham as "not true fans" and deemed it "unacceptable".
Vicario was booed by his own supporters after his howler in a shambolic opening half against Fulham in which Spurs conceded twice in the first six minutes, with a second-half revival not enough to avoid a 2-1 defeat.
Already trailing from Kenny Tete's third-minute deflected opener, a moment of madness from the Italian goalkeeper less than three minutes later gifted possession to Harry Wilson after running some 25 yards off his line, and the Fulham midfielder punished his poor clearance with a stunning strike into the unguarded net.
Frank told Sky Sports: "I didn't like that our fans booed at him [Vicario] straight after and a few times he touched the ball. They can't be true Tottenham fans because everyone supports each other when you are on the pitch.
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"And we do everything we can to perform. After, fair enough, boo, no problem. But not during. That's unacceptable in my opinion."
Spurs' horrific start proved insurmountable and condemned them to a 10th home league defeat of 2025, their joint-worst tally in a calendar year with Brentford and Liverpool still to come to north London in December.
Frank blamed the pressure of that unwanted home record for their lack of an immediate response, only improving after half-time and finally threatening a comeback - though it would never materialise - through Mohammed Kudus' thunderous strike on the hour mark.
"This game we lost in the first six minutes. We just need to keep working," Frank said.
"After that, we rushed the first half in many ways. We wanted to come back into the game but couldn't do it in the first half, but we got much better in the second half. We got a bit of momentum, created more chances and opportunities, but couldn't get the second goal.
"It was an emotional performance in the second half, and I think that's quite normal. We know that we badly want to win at home, so when it's not going your way, it is hard. That's why you need to stick to the plan, be cool and not stress. It is easier said than done."
Vicario on boos: It's a part of football
Meanwhile, Vicario said fans have the right to boo the players when he faced the cameras after the game.
"It's part of football. I'm a big man and older," he told Sky Sports.
"We can't be influenced by the situation in the stands. The fans have the right to do what they think. It's on us to stay calm.
"We have to focus on ourselves
"We are lacking in a little bit of composure and calmness at the moment. Today is a bad defeat and tough to accept."
The unhappy home of Spurs' palatial surroundings
Tottenham suffered their 10th home defeat of 2025 in the Premier League, with this now their joint-most home league defeats in a single calendar year in club history (also 10 in 1994 and 2003).
Spurs have picked up just 14 points on home soil across the last 12 months, the lowest of any ever-present Premier League team and six behind the second-lowest total, West Ham.
Of the three teams they have beaten in that time, Southampton were relegated with 12 points, Manchester United finished 15th and Burnley, their only home win this season, are currently second-bottom of the Premier League.
Tottenham have faced 37 more shots and 27 more shots on target than they have attempted across those 12 months at home.
Fulham's 2-0 lead as of the sixth minute marked the earliest that Spurs have ever conceded two goals in a Premier League home match.
Tottenham have lost four consecutive home London derbies for the first time in the Premier League (twice vs Chelsea, Crystal Palace and Fulham).
Dawson: Spurs need to be realistic
Former Tottenham defender Michael Dawson on Saturday Night Football:
"It was always going to improve from last season [in the Premier League]. They are 10th now but only four points off the top four, so that's where you have to be realistic.
"Did I expect them to finish in the top four this season? I didn't. I thought top six was realistic with Frank going in.
"With what he did over the last four or five years at Brentford, we can't now just say Frank isn't a good coach.
"The performances have been well below par at home. It is that creativity. It is hard for Thomas but he has only been in the building a blink of an eye, you have to give him a chance but you have to see an improvement.
"They are only four points off top four. Top six was a realistic aim. Thomas Frank is a good coach because we have seen it for years, but a big club brings expectation and scrutiny.
"This group of players aren't playing to the levels I expect them to be."