Costa has been troubled by the hamstring problem for some time .
Mourinho believes it was exacerbated by Spain coach Del Bosque fielding the player for back - to - back games against Slovakia and Luxembourg at the start of October .
Costa has been troubled by the hamstring problem for some time , but Mourinho believes it was exacerbated by Spain coach Del Bosque fielding the player for back - to - back games against Slovakia and Luxembourg at the start of October .