Tottenham Hotspur scored after just 57 seconds against Wolverhampton Wanderers on Sunday but Jose Mourinho's men paid for defensiveness during the rest of the game when the hosts deservedly equalised in the dying minutes.
Seeking to revive their faltering push for a first Premier League title, Spurs had a dream start when French midfielder Tanguy Ndombele received the ball well outside the box to drill a low shot past Wolves goalkeeper Rui Patricio.
"We conceded a poor early goal ... When you are not focussed for a half second, it's a goal," Saiss said. "After, it's harder when you play a team like Tottenham to come back. Even with the draw, we deserved more because we created a lot of chances."
Spurs, who topped the league earlier in December, have now taken just two points from their last four games and are fifth in the Premier League, six points behind leaders Liverpool.
"I am frustrated with the result. We had control of the game. But we had 89 minutes to score goals, and we didn't," Mourinho said, chiding his team for lack of ambition.
Wolves, who are now 11th on 21 points, were watched by their Mexican striker Raul Jimenez for the first time since he fractured his skull last month.
Without him, Wolves have struggled and are looking to Portuguese teenager Fabio Silva for goals.
He came close in the first half with a snap shot that went just past the post, was charged down by Spurs goalkeeper Hugo Lloris in the second, and missed another close-range chance at the end which would have won the game for Wolves.
"I'm proud, really proud, because it's very hard how we started the game," said Wolves manager Nuno Espirito Santo, who fielded seven Portuguese countrymen in his starting lineup.
"After that, we played a good game."
Wolves have made a habit of comebacks, while Spurs are repeatedly failing to hold leads, to the anger of their demanding manager Mourinho.