"The reality is you can not only play for 45 minutes, we are a Champions League team, into the quarterfinals", said Pochettino, whose side beat high-flying Borussia Dortmund 1-0 in Germany on Tuesday to complete a 4-0 aggregate win.
But they paid the price for only taking a slender advantage into the break.
"You can use the first half as an example of (positive) arrogance, playing with intention, focus, concentration, we matched them in everything and we were much better". After all, this is a team that can deliver two incredibly impressive displays against the leaders of the Bundesliga and, within the same period, lose at Burnley and Southampton.
For Spurs, it was a head-scratching loss given the way they dominated the first half. Their defence were rarely troubled while in midfield Dele Alli simply picked up from where he had left off in his first appearance since sustaining a hamstring injury in late January.
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Assistant manager Jesus Perez, first-team coach Miguel D'Agostino and goalkeeping coach Toni Jimenez will be directing from the touchline today, with Pochettino communicating by walkie-talkie. In truth the 47-year-old could have kept his phone in his pocket.
And if they do secure survival this season, Hasenhüttl hopes the club can start looking up the table again.
The only positive for Southampton was that it was only 1-0 at the half-time break and after Hasenhuttl brought Shane Long and Josh Sims on for the restart, they were much more unsafe as they threatened with pace and running they had not shown before.
And it was that panic, allied to a general drop in intensity by the visitors, that led to Southampton's equaliser.
After producing a similar free-kick the game prior against Manchester United, James Ward-Prowse found himself on the winning side with an equally-magnificent set-piece against Spurs. "It is so hard to understand why we changed so much from the first half to the second", Pochettino added.More news: USA to end trade preferences for Turkey, India
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