Third-placed Tottenham's second successive home defeat left them nine points behind league leaders Liverpool and should Manchester City beat Wolverhampton Wanderers on Monday to go five clear, it will surely be a two-horse race for the title.
Marcus Rashford's 44th-minute goal proved decisive as Tottenham threw everything at United after the break with visiting keeper David De Gea making 11 saves -- several of them in the world-class category.
Tottenham were chasing a first league double over United since the 1989-90 season after a 3-0 away victory in August but despite his obvious disappointment Pochettino said Sunday's performance was much better than the one at Old Trafford.
"I am so pleased and I'm proud," Pochettino, who is being strongly linked to the Manchester United manager's job, told reporters. "For me it was one of the best performances that I saw since I've been here and the best 45 minutes.
"I think David de Gea made 11 saves, which is unbelievable. We didn't create much in the first half but we dominated.
"Overall, it was fantastic. My feeling today is the opposite of when we won at Old Trafford. After we won that game 3-0, I wasn't happy but today after the defeat I'm very pleased with the performance.
"That's the way we want to build a team for the future, to be close to win the title.
"I'm not happy with the result, of course, but very happy with the reaction after conceding the goal. We created more than enough chances to win the game. In the end, that is football."
A sixth win out of six in all competitions since taking over from Jose Mourinho means United's interim manager Ole Gunnar Solskjaer's chances of taking the full-time post are increasing.
Pochettino moving to Old Trafford still seems likely, however, even if the Argentine, unsurprisingly, refused to be drawn into that discussion after the game.
"I don't think it's ethical to talk about what he's doing or what I'm doing," Pochettino said. "You can only talk about today's game. And today we were better.
With Harry Kane suffering an injury in stoppage time, Moussa Sissoko limping off before halftime and in-form South Korean Son Heung-min jetting off to the Asian Cup, Pochettino's stretched squad now face a key test over the coming weeks.
They remain third but Chelsea are only one point behind while Arsenal and United are seven adrift.
United look re-born under Solskjaer, however, and the Norwegian believes the top-four chase is on.
"We had to beat them today if we were to have a chance to catch them," he said. "We were 10 points behind and now it's seven. That's catchable. Thirteen is impossible, 10 is difficult, now we have a chance."
"I'm just doing my job every single day here until my contract runs out at the end of June and then I'll have a holiday. Not thinking about (the full-time job) whatsoever." (Reporting by Martyn Herman Editing by Ian Chadband)
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