The 21-year-old Danish playmaker has agreed a five-year deal at White Hart Lane and is expected to complete his move by the end of the week.
And de Boer believes Eriksen will be a big success at Spurs, but admits he will leave a big whole in his Ajax side next season.
He told de Telegraaf: “Eriksen will go and he can be a success at Spurs.
“But this is a huge loss for us. He is very important to the squad.”
Eriksen’s arrival is thought to be as an alternative to former target Willian, who opted to sign for Chelsea despite already passing a medical with Spurs.
Spurs boss Andre Villas-Boas has spent over almost £90million in improving his Spurs side this summer as he attempts to build a side capable of finishing in the top-four ahead of London rivals Arsenal, while it is expected that Gareth Bale will complete his world-record £85million move to Real Madrid by the end of the week.
Meanwhile, Spurs have also been linked with Lazio’s Brazilian playmaker Hernanes, who is yet to sign a new contract at the Stadio Olimpico.
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