Tottenham Hotspur midfielder Rodrigo Bentancur's header salvaged a 1-1 draw against Sporting to keep the London side in control of Champions League Group D but the game ended in chaotic scenes as Harry Kane's last-gasp effort was disallowed on Wednesday.
Victory for Spurs would have booked their place in the last 16 with a game to spare and they thought they had sealed it with almost the last kick of the game when Kane fired in from close range after Emerson Royal's header across goal.
It sparked wild celebrations on the touchline but joy turned to anger as a VAR check that lasted several minutes ruled the goal out for offside -- prompting a furious reaction from Spurs manager Antonio Conte who was sent off for his reaction.
Conte's team will now have to avoid defeat at Marseille next week to qualify for the knockout phase, while Sporting's reprieve means they can also still progress.
"I thought because [Emerson's header] went backwards and hit a defender it was a different phase of play," Tottenham defedner Matt Doherty said of the decision that left the majority in the stadium scratching their heads.
"I'll have to look at the rule book. A few of us don't have a clue what happened."
The result left Tottenham top of a desperately tight group on eight points, with Sporting and Eintracht Frankfurt, who beat Marseille 2-1, on seven. Marseille have six points.
Spurs will qualify for the last 16 if they avoid defeat in Marseille on Tuesday when Sporting host Frankfurt also needing a point to guarantee a place in the knockout stage. If Tottenham lose in France they will be out of the competition.
Conte admitted his side were poor in the first half but questioned whether the VAR decision would have been given against one of Europe's heavyweights.
"I would like to see this type of decision with a top team, in an important game, I would like to see if VAR is so brave to take this decision," the Italian said.
Tottenham began the match on the back of successive Premier League defeats which stopped their early-season momentum.
They were awful in the first half against Sporting, slow in possession and cumbersome in attack and the visitors dominated.
Tottenham were vastly improved after the break and peppered the Sporting goal in their desperate search for an equaliser with keeper Antonio Adan making sharp saves from Eric Dier, Son Heung-min and Doherty.
Sporting substitute Flavio Nazinho spurned two great opportunities to make the points safe -- first denied by Lloris and then shooting wide of an open goal - and in the 80th minute those misses looked even more costly as Tottenham levelled.
Ivan Perisic swung in a corner and midfielder Bentancur rose highest to head powerfully past Adan.
There was still more drama to come with Lloris forced into a great to deny substitute Fatawu Issahaku before Kane thought he had stolen it for the hosts.
"Last year we had some luck in certain moments, this season has been a very difficult season, so I hope for the best and he [Kane] was offside and it was a good moment," Sporting coach Ruben Amorim said of the final twist.
"It was a very good first half and then the second half we were tired, but we suffered as a team."