Tottenham Hotspur manager Mauricio Pochettino has told Sky Sports the club will make signings but will only bring in players who can challenge for a place in his starting XI.
Spurs -- the only Premier League club yet to make a summer signing -- begin the new season with a trip to Newcastle on Sunday.
Last summer, they signed attackers Vincent Janssen, Georges-Kevin Nkoudou and Moussa Sissoko for a combined £58 million, but the trio started just 15 league games between them and only Janssen scored.
Pochettino said Spurs would make signings before the Aug. 31 transfer deadline but warned: "It's not an easy job.
"We need players who can challenge our starting XI, players who believe in themselves and think: 'OK, I can challenge Dele Alli, I can challenge Harry Kane.'
"Harry Kane knows very well from when he was behind [Roberto] Soldado and [Emmanuel] Adebayor what happens when you're not focused for a moment, if another player is behind you pushing for a chance if you don't give your best.
"You cannot guarantee that they [new signings] will play, but you can guarantee the tools to challenge our current players. If they are better and they deserve to play, they will play."
Pochettino said Spurs "need to bring new energy and strengthen our squad, everyone knows that," adding: "If you look at the history of Tottenham in the last few years, we always spend at the end of the window.
"Chairman Daniel Levy is working hard with the chief scout [Steve Hitchen], we are working hard to deliver and try to add the strength we need to fight in four competitions next season."
The Spurs boss added that the transfer market "is a little bit crazy, but you cannot stop the evolution of football," and stressed: "We will find the right players to challenge."
Tottenham finished third in 2015-16 and second last season and, asked whether they could go one better and win the Premier League, Pochettino added: "Of course. That is our dream. I am always very positive and so excited to start again.
"We have many challenges ahead, including playing at Wembley [the club's home for next season], but we are ready to compete on Sunday at Newcastle."