Match ends, Middlesbrough 1, Tottenham Hotspur 1.
Jose Mourinho admitted his Tottenham side were "in trouble" but praised their reaction as they came back to draw at Middlesbrough and force an FA Cup third-round replay.
Spurs named a full-strength team, bar the injured Harry Kane, but trailed to the Championship side when Ashley Fletcher ran on to George Saville's ball and slotted home.
Lucas Moura saved the visitors with a fine header from Serge Aurier's cross.
"When we were losing 1-0 without strikers or the power to play inside their defensive line with lots of bodies and great soul, at that moment I had the feeling of 'we are in trouble'," Mourinho told BBC Sport.
"But then everyone reacted. I reacted. The boys reacted. Giovani lo Celso and Erik Lamela [who came on in the 56th minute] helped us a lot. If one team has to win, it has to be us. We played well very in the last 20 minutes, we were just missing a second goal."
Mourinho thought Fletcher was offside for Boro's goal, but actually seemed pleased that the video assistant referee system was not in action.
"The Middlesbrough goal is offside. VAR would give [the offside decision]. But the game was good. The referee was Stuart [Attwell], not some guy in an office 200 miles away," he said,
Moura twice went close to a winner, with goalkeeper Tomas Mejias stopping his long-range shots.
Aurier could have won the game for Mourinho's side in the closing minutes but fired an effort well over the bar.
Fletcher had an earlier chance to make it 2-1 to Middlesbrough - managed by one-time Spurs defender Jonathan Woodgate - but shot straight at Paulo Gazzaniga.
The replay at the Tottenham Hotspur Stadium will be on Tuesday, 14 January - unless it gets moved for TV.
"We wanted to win but we knew it would be difficult. We managed to bring the game to our stadium. It's a game we don't need, our squad is short with so many problems - but it's a game at home and we have to go for it," said Mourinho.
The fourth-round draw takes place on Monday at 19:35 GMT on BBC One and the iPlayer before Arsenal's game against Leeds.
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Spurs' strongest team was almost not enough
Mourinho said he would not forgive himself if he had named a weakened team against a side who had won their previous four Championship games. But even his first-choice XI - with Son Heung-min returning from suspension - was only enough for a draw.
"We knew the way they play, long balls to the strikers," he said. "Because we have no striker, I wanted to give Son and Lucas the chance to play together as a more dynamic double striker pair - different to Harry Kane. But Lamela and Lo Celso gave us more ball."
Spurs have not won a trophy in more than a decade - since Woodgate scored the winner for them in the 2008 League Cup final against Chelsea, with Boro assistant Robbie Keane also playing in that game.
And in Mourinho, they have a manager who has won plenty of trophies, including the 2007 FA Cup with Chelsea, as well as domestic cups in Spain, Italy and Portugal.
However, they are suffering plenty of defensive problems - and have conceded first in eight of his 12 games in charge. Mourinho's sides - including at the end of his spell at Manchester United - have only kept one clean sheet in their past 17 matches.
Spurs defenders appeared to switch off as Fletcher controlled Saville's ball, before the midfielder ran through and finished. He was borderline offside, but there was no video assistant referee at the Riverside to try to dissect it down to the nearest millimetre or armpit.
They deserved their equaliser as Moura headed home, before the Brazilian was frustrated by Mejias on a couple of occasions.
'We knew we'd get chances' - Boro reaction
Middlesbrough manager Jonathan Woodgate to BBC Sport: "I'm really pleased. They gave everything they had. We were against a side who reached the Champions League final and have an unbelievable manager. So for us to go toe to toe with them, which we did at times, [was good]. I'm disappointed to come out 1-1.
"I wanted them to press higher [in the second half] and not be so deep. That was the key. We knew we'd get chances. They haven't kept a clean sheet away from home.
"Jose Mourinho is an incredible manager. He made changes and got the result. I can learn from him. He's a fantastic person.
"We want to try to get to the next round. There's no point competing if you don't think you can win."
- 22SavilleBooked at 85mins
- 33CoulsonSubstituted forJohnsonat 67'minutes
- 19RobertsSubstituted forGestedeat 69'minutes
- 11FletcherSubstituted forNmechaat 76'minutes
- 8WinksSubstituted forLamelaat 56'minutesBooked at 85mins
- 20AlliBooked at 45mins
- 19R SessegnonSubstituted forLo Celsoat 56'minutes
- 27Lucas Moura
- 7Son Heung-Min
- 6D Sánchez
- 18Lo Celso
- Stuart Attwell
- Shots on Target
Second Half ends, Middlesbrough 1, Tottenham Hotspur 1.
Foul by Erik Lamela (Tottenham Hotspur).
Adam Clayton (Middlesbrough) wins a free kick in the attacking half.
Foul by Christian Eriksen (Tottenham Hotspur).
Lukas Nmecha (Middlesbrough) wins a free kick on the left wing.
Lucas Moura (Tottenham Hotspur) wins a free kick in the defensive half.
Foul by Djed Spence (Middlesbrough).
Corner, Tottenham Hotspur. Conceded by Marcus Tavernier.
Attempt missed. Serge Aurier (Tottenham Hotspur) right footed shot from the right side of the box is too high. Assisted by Erik Lamela.
Offside, Middlesbrough. Dael Fry tries a through ball, but Rudy Gestede is caught offside.
Erik Lamela (Tottenham Hotspur) is shown the yellow card.
George Saville (Middlesbrough) is shown the yellow card for a bad foul.
Giovani Lo Celso (Tottenham Hotspur) wins a free kick in the attacking half.
Foul by George Saville (Middlesbrough).
Corner, Tottenham Hotspur. Conceded by Tomás Mejías.
Attempt saved. Lucas Moura (Tottenham Hotspur) right footed shot from outside the box is saved in the top centre of the goal. Assisted by Dele Alli.
Corner, Tottenham Hotspur. Conceded by Dael Fry.
Substitution, Middlesbrough. Lukas Nmecha replaces Ashley Fletcher.
Corner, Tottenham Hotspur. Conceded by Patrick McNair.