De Bock has left Elland Road on loan to join Belgian side KV Oostende.
Leeds' new system has been down to the players improved fitness.
Leeds United parted company with Heckingbottom less than four months after hiring him.
The Leeds United-owned attacker didn't play a single minute under Paul Heckingbottom.
However it seems that neither the Everton Under-23s coach nor Heckingbottom will succeed Simon Grayson at Bradford City.
Bookies' favourite Paul Heckingbottom is in contention to become the new manager of Bradford City, just days after he was sacked by Leeds United.
Leeds United recently parted company with Paul Heckingbottom.
Paul Heckingbottom is no longer in charge of Elland Road outfit Leeds United.
After leaving Championship giants Leeds United, could Paul Heckingbottom make a shock return to League One club Bradford City?
Leeds United have sacked Paul Heckingbottom, just four months after he left Championship and Yorkshire rivals Barnsley for Elland Road.