Answer
Winning four consecutive titles made De Boer the first manager to do so in the Eredivisie. He did so with Ajax, a Dutch football club. De Boer was the manager of Ajax from 2010 to 2016. He won the Eredivisie title four times in a row with Ajax, from 2011 to 2014. De Boer is the only manager in Eredivisie history to have won four consecutive titles.