Whether he could do it or not with a rider bearing down on him was unknown but they would both find out.
Being so stressed with a rider bearing down on him he wasn't sure whether or not he could do it but they would both find out soon.
mnli hypothesis: Being so stressed with a rider bearing down on him he wasn't sure whether or not he could do it but they would both find out soon. premise: Whether he could do it or not with a rider bearing down on him was unknown but they would both find out.