Definition of set (or rock) someone back on their heels in US English:

set (or rock) someone back on their heels

phrase

  • Astonish or disconcert someone.

    • ‘But the home side seemed galvanised early on, some ferocious tackling rocking Queensland back on their heels.’
    • ‘They counter attack from deep in their own defence and our forwards should have been tackling them with a ferocity that would have disrupted them and rocked them back on their heels near their own lines.’
    • ‘A tremendous drive set them back on their heels, forcing them to concede a penalty.’
    • ‘An early goal could have rocked Brighton back on their heels.’
    • ‘Then, just as the team seemed to be establishing a foothold, two interceptions set them back on their heels.’