Swansea forward Michu has undergone surgery on his injured ankle and will be out for six weeks.
The forward has been told he needs surgery on the injury which has troubled him for much of the season.
And with Nathan Dyer also out for several weeks, Swansea boss Michael Laudrup now plans to look for reinforcements in January.
Speaking at his press conference ahead of the Boxing Day trip to Chelsea - the first in a run of five tough games in 17 days - Laudrup said: "What has happened in the last couple of weeks has changed things.
"We will probably do something now in January and try to add something that we don't have in certain positions.
"The numbers are a bit down and that is risky for the last four months of the season."
Michu has scored half as many goals this season as the 12 he had by the same stage last year, and his last in the Premier League came at Crystal Palace three months ago.
"It's not good news," Laudrup said of the injury. "Unfortunately it has been confirmed that he will need an operation.
"It can be done in the next week and he should be back playing in around a month and a half."
Among the players Laudrup has been linked with a move for is Liverpool striker Iago Aspas, who he actively pursued last summer.
But Laudrup believes it may prove a difficult deal to pull off.
"He is an interesting player, he was on our list in the summer. But he is at Liverpool and they have injuries too," he said.