Tottenham are in talks with highly-rated attacker Eriksen about a move to White Hart Lane after Ajax granted them permission to speak to the 21-year-old.
Eriksen has been linked with a host of Europe's top clubs after impressing for Ajax and Denmark over the last couple of years.
De Boer is disappointed at the prospect of losing his star player and believes he will be a major success in the Premier League if he does end up joining Tottenham.
"His departure will be an enormous loss, Chris was very important for us," De Boer told De Telegraaf
"We always have work in a good way. Players who are that good and also the ideal professional are, for a coach, the most ideal players."
Asked if he thought Eriksen would succeed in England, De Boer said: "It would surprise me if that won't happen."