Mauricio Pochettino believes Tottenham's fate in the Champions League next season will depend on the signings they make this summer.
Spurs have already secured automatic qualification for Europe's premier competition but they will need a deeper squad, having rotated heavily during this year's Europa League.
Borussia Dortmund took full advantage of Tottenham's weakened line-up, winning 5-1 on aggregate in the last 16, as Pochettino's men threw everything into their challenge for the Barclays Premier League title.
To compete fully on both fronts next season, Pochettino believes Spurs will have to strengthen further in the transfer window.
"We need to improve our squad - this is very clear," Pochettino said.
"Me, our supporters, our players, our squad - we are all agreed that we need to improve. It's a different level to play in the Champions League.
"To play in the Champions League, the Premier League and the cups, it's important to have a very good balance. We need to improve our squad.
"Replicating this season again is our challenge. For that, we need to improve our squad, to reduce the gap. The Champions League demands a lot of energy, more than the Europa League."
Tottenham currently boast the youngest squad in the division but it has been suggested the team could benefit from some added experience.
Pochettino admitted on Thursday his side needed to improve their mental resilience but the Argentinian suggested the club would still look to youth this summer.
"I think today at Tottenham, when you analyse the squad, you need to add not only the football side but the human profile," Pochettino said.
"You have some limitations. But it's true that younger players fit better, than older players. This is how our squad is different today than maybe a few years ago."
Tottenham are likely to need only a draw at already-relegated Newcastle on Sunday to finish second in the table, which would represent the club's highest top-flight placing since 1963.
A point should also see them end them season above north London rivals Arsenal, who sit two points behind and host rock-bottom Aston Villa, for the first time since 1995.
It would tie up a remarkable campaign for Spurs, whose primary aim was to finish in the top four, although Pochettino says there are still lingering regrets from not winning the league.
"It's difficult now to explain the feelings because we feel disappointed after the Chelsea game because in this moment we put ourselves out of the race for the title," Pochettino said.
"Now to be second in the league is very important for the club. It's important to go straight away to the group stage of the Champions League because it was a target at the start of the season.
"We need to feel very happy and very proud. When you analyse all the things that happened during the season from the beginning, to finish second is a great achievement for the club."