As per The Wall Street Journal:
"Germany’s “powerful finance minister, Wolfgang Schäuble, has long believed that Greek politicians aren’t capable of adapting Greece’s economy to the rigors of euro membership. Mr. Schäuble sees Greece as the weak link not only for Europe’s common currency, but also for Europe’s border controls against migration, and would welcome a new debate about a Greek exit this year, say people familiar with his thinking.”This should come as no surprise to anyone. More to the point, the need for a resolution to the Greek question has been given added impetus by the migrant crisis. The position of the Schengen border is now being used as means to pressurise Greece to implement the agreed reforms.
The bottom line is that Greece must implement the reforms or, in effect, leave.