LONDON -- Mauricio Pochettino says Tottenham must improve their squad this summer and be stronger "mentally" if they are to compete in the Champions League next season.
With one league match remaining, Tottenham are guaranteed a top three finish and entry into the Champions League group stage for the first time since the 2010-11 season.
Spurs were challenging for the title until the 2-2 draw at Chelsea a fortnight ago confirmed Leicester City as champions, but they were beaten 5-1 on aggregate by Borussia Dortmund in the Europa League round-of-16 earlier in the season, after Pochettino had heavily rotated the squad.
Pochettino has previously said it is not his "philosophy" to buy players, preferring instead to promote from Spurs' academy, but he admitted the club must strengthen the squad in order to compete on multiple fronts.
"We need to improve our squad -- this is very clear," the Spurs manager told a news conference. "Me, our supporters, our players, our squad -- we are all agreed that we need to improve.
"It's a different level to play in Champions League. To play in the Champions League, the Premier League and in the cups, it's important to have a very good balance. We need to improve our squad.
"This is our challenge -- to reduce the gap. The Champions League demands a lot of energy, more than the Europa League. It's a very different competition. For that, we need to ensure we have a strong squad to compete in every competition."
Spurs have squandered leads in their last three Premier League matches, drawing to West Brom and Chelsea before losing to Southampton.
Pochettino's side have lost 20 points from winning positions this term -- more than any other Premier League club -- and they have squandered leads on nine occasions, including in both North London derbies.
The Spurs manager said he would focus on improving the mentality of his young squad next term.
"We don't only need to assess the last few games," Pochettino said. "To move on, to grow up and to improve, we need to learn. Next season, more than tactics or physical condition, we need to improve our mental state. This is our challenge for next season.
"For us, it was the first season all together with this young group that plays for big things. If you analyse all the games, we were always better than our opponents, but it's not always about playing well sometimes. There's another game you need to manage too. We need to improve the mental state to be more strong.
"You need to cross this line. In English it's difficult to explain, but in my mind, this is my idea. Maybe my challenge is to improve my English for next season!
"Many things we have in our mind to improve. We need to deliver from day one next season."