Sociedad striker jinx hits again
The 22-year-old, who was signed from Ulsan during the summer, severely damaged ligaments in his right ankle after a clash with French defender Lionel Potillon in a training session on Friday.
It is believed Lee has partially torn the ligaments, but will not need to undergo surgery on the problem.
However, early tests carried out by the Basque club estimate that the pacey striker will be out of action for at least a month.
Sociedad's frontline have been blighted by injury problems this term, Turkish star Nihat Kahveci has yet to make an appearance, while Darko Kovacevic sustained a leg injury in this week's 1-1 draw with Celta Vigo and will be out for two weeks.