Tottenham Hotspur manager Antonio Conte (AP)
Club-record signing Tanguy Ndombele, who cost £55 million ($74 million) in 2019, returned to Lyon on loan while fellow midfielder Giovani Lo Celso headed to Villarreal for the rest of the season.
Spain winger Bryan Gil, who only signed for Spurs in July, went to Valencia on loan and Dele Alli signed for Everton on an initial free transfer, with add-ons that could go up to £40 million.
Tottenham manager Conte, who was appointed in November, said the departures showed Spurs had previously made errors in the transfer market.
"It was strange because it means something went wrong in the past," he said on Friday. "It was strange, I repeat in January to send four on loan (including Jack Clarke to Sunderland), and sell one player.
"It means maybe in the past you have to see what you did. And maybe to understand that there were some mistakes in the past."
The Italian said Tottenham must pay more attention in the future when it came to new signings to close the gap to their Premier League rivals.
"It becomes of fundamental importance," he said. "Otherwise, when you try to improve the quality of your team, you drop the quality of your team.
"We know very well there are many teams ahead of us. To catch up with them we need time and patience to work hard. Especially in the transfer market, we have to make not big mistakes."
He used the arrival of Gil as an example of a misjudged signing, saying the 20-year-old, although talented, did not fit the profile of a Premier League player.
"In this moment, for sure this league is very tough," he said. "This league is different. If you compare this league with other leagues, you play another sport here.
"For this reason when you go to sign a new player, you have to consider many aspects. Not only one aspect, if he shoots well or makes an assist -- you have to consider a lot of situations because this league is very difficult."
Spurs were able to bring in Juventus pair Dejan Kulusevski and Rodrigo Bentancur at the end of the transfer window and Conte said they would improve his squad.
They will both be involved against Brighton in Saturday's FA Cup tie, but will not start.
"For sure, the squad is now more complete," Conte said. "We tried to fill the right role with one midfielder in Rodrigo Bentancur and Dejan Kulusevski can play as a No. 10 and also he can play as a wing-back."
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