The 43-year-old, who has been mooted as a potential successor to the former Barcelona boss, has backed the coach's decision to resign and wished him a speedy recovery from cancer
And De Boer, who played at Camp Nou from 1999-2003, is glad Vilanova has stepped away from the Catalunya spotlight to recover, saying his health is the "most important thing."
"Yes of course it is very sad for him, because he is a very good coach," De Boer told reporters. "But with his illness he couldn't perform what he wanted to, I think. But maybe it is the right choice right now for him because you cannot be totally focused for the team.
"Hopefully he will recover very soon and be able to coach at whatever level [he wants]. The most important thing is the health of Tito."
De Boer has been suggested as one of the potential candidates to replace Vilanova, along with the likes of Marcelo Bielsa and Luis Enrique.