Wellens has impressed Nigel Pearson since signing from fellow Championship club Doncaster in the summer and has started all eight league matches thus far.
However, Wellens' hamstring injury will not be a major concern for Pearson when selecting his side to face tough opponents Preston N.E, Andy King will be available and should line up alongside Matt Oakley.
The pairing of King and Oakley were dynamic in the Foxes League One winning campaign last season and should continue their strong relationship in Wellens' absence.
Preston play host to Tottenham tonight in the Carling Cup third round after knocking City out in the second round with a 2-1 win and Saturday's game will be a good chance for the Foxes to seek revenge for that loss.