You hired a foreign worker, and within his probationary period you find him useless and not qualified with the job. What will you do then?

First of all nobody is useless.  Every person is unique and comes with his set of skills and experience. 

In this particular case I would investigate on the following grounds:

How did this candidate get hired i.e. right from source of CV, screening of CV’s, interview feedback of candidates, would also validate mode of interview candidate (just to ensure no proxy interviews has been done) net net was the candidate evaluated properly for the said role ?

Once selected and offered, Have we assigned him the right work based on his experience, qualification and interview feedback  are there any other factors impacting his performance on the job.

If in spite of above due diligence done we come across a candidate who is probably not performing the job then I would recommend one to one chat / feedback session and a PIP program to be fair to the said candidate as well.

Before confirming as a regular staff, as a supervisor I will discuss with supervisee and recommend to HR do not confirm him or her due to s/he is uncapable to carry out the job objective as well as organization. Finally, he will not be a confirm or regular staff.