Buttner, 23, was expected to join Premier League side Southampton last month but the move broke down after a third party became involved with the deal and wanted a percentage of the transfer fee.
The midfielder has since been placed in the reserves at Vitesse as the GelreDome club look to cash in on the Dutchman, sparking attention from Fulham and Bundesliga outfit Hannover.
Buttner’s agent Alexander Busac said: “There is a lot of interest. Hannover and Fulham are serious.”
Buttner scored five goals in 32 Eredivisie matches last season and was part of Bert van Marwijk’s prelminary Netherlands squad to go to Euro 2012.
Doncaster took a major step towards securing their Sky Bet League One survival by beating Bradford 2-0.
Southampton manager Mark Hughes was delighted to see his new side reach the FA Cup semi-finals but also warned that the Premier League remains a concern.
Borussia Dortmund winger Andre Schurrle was delighted with the team's hard-fought 1-0 Bundesliga victory over Hannover 96 on Sunday afternoon.