sorry - English is not my first language. (Not fixing the comment to keep yours relevant)

I think my question is being taken the wrong way. Let me try asking again: I have work X to get done. I have a team member who I would like to work on this. I ask them to estimate the work, validate the estimates and then track against the same. In the weekly status calls, if they are behind schedule, can not give a justifiable reason for being behind (like personal reasons, unexpected technical complexity, hardware issues); how does the group manage?