The Wales international midfielder was forced off midway through the second half of the 2-0 defeat at Bristol City on Saturday.
"I don't think it is too serious because if it is very bad then you can hardly walk off the pitch and he was jogging, so I don't think it is too bad," said Eriksson.
"We had to react quickly because if we had left him on it could have been worse and he could be out for five or six weeks, and we don't want to be without him for that long."
Source: PA
Source: PA