The Ajax boss, who has been mooted a potential successor to the Camp Nou post, has wished the coach a speedy recovery from cancer
De Boer, who played at Camp Nou from 1999-2003, believes Vilanova's return to health is the most important thing and is glad he has stepped away from the Catalunya spotlight to recover.
"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 rumoured as one of the potential candidates to replace Vilanova, along with the likes of Marcelo Bielsa and Luis Enrique.