Tottenham slipped to a 2-1 defeat to Leicester City on Tuesday night.
Two superb first half goals from Jamie Vardy and Riyad Mahrez put the hosts two ahead before to send Claude Puel's side into the break with a two-goal lead.
Harry Kane pulled one back for the visitors with ten minutes left on the clock, but it wasn't enough to salvage a point against an organised Leicester side.
In a post-match interview with the BBC, Pochettino said: "we didn't play in the way we normally play and I think the first half was poor.
"We were poor first half. We feel very disappointed with our performance. We started the game in the right way.
"To be critical with ourselves, we need to improve in the way we start. It happened against West Bromwich (Albion) and it happened against Dortmund."
Poor first-half performances are proving to be a recurring problem for Pochettino this season, with Salomon Rondon's fourth minute goal last weekend handing Spurs an uphill struggle and two goals prior to the break against Arsenal proving costly in the North London derby.
The defeat could potentially see spurs drop down to 7th place in the Premier League table should Liverpool and Burnley both win on Wednesday night.
The North London club now find themselves 13 points off table-toppers Manchester City having played one more game. All chances of a title push are now practically over, with the focus now surely on securing Champions League football.