Mauricio Pochettino blamed wayward finishing for Tottenham's surprise 1-0 defeat to West Brom at The Hawthorns.
Harry Kane had Spurs' best chance of the game, firing at Ben Foster from close range in the first half, while Victor Wanyama and Christian Eriksen also tested the Albion goalkeeper with efforts from distance.
However, Spurs' failure to make the breakthrough was punished emphatically when Jake Livermore prodded in the winner in the 92nd minute in what was West Brom's only shot on target.
When asked whether Spurs should have won the game, Pochettino said: "Absolutely but we missed chances to score. In football, you can dominate, have the option to score but then you have to be clinical and today was not good. Our finishing wasn't good and we are very disappointed.
"Against a team like West Bromwich [Albion] it is always possible that can happen because they are very physical and work very hard and are good at set-pieces.
The result has reopened the top-four race as Chelsea can move two points behind Spurs with two games remaining should they win their game in hand against Liverpool on Super Sunday, live on Sky Sports.
But Pochettino insisted that securing Champions League football is still in Spurs' hands with two home games against Newcastle and Leicester to come.
"Still we have in our hands the possibility to be in the top four," he said.
"We didn't concede many chances, all of them came from set-pieces but that is normal, we knew very well how they play. If you want to be in the top four and challenge for big things, in this kind of game you have to score and not arrive in the last minute at 0-0 because the situation can happen.
"We have two games at Wembley to play - on Wednesday and Sunday - and it [finishing in the top four] is in our hands. After these two games, if we don't then we don't deserve to be in the next Champions League."
A terrible day for Spurs was compounded when Jan Vertonghen - a contender for the club's Player of the Year award - limped off with an injury shortly before West Brom scored the winning goal.
When asked how severe the Belgium international's injury was, Pochettino said: "At the moment it's impossible to say. We hope not. He twisted his ankle and we hope it is not a big issue."