Swans boss Michael Laudrup has confirmed that Michu will need ankle surgery, ruling the Spaniard out for up to six weeks.
The 27-year-old, who has scored six goals this season, has had both ankle and knee problems during the current campaign.
Meanwhile, with Nathan Dyer also sidelined until at least February, Laudrup also confirmed that he would look to do some business in the upcoming January transfer window.
“It’s not good news,” he said. “Unfortunately it has been confirmed that he (Michu) will need an operation. The good news is that it can be done in the next week and he should be back playing in around a month and a half.
“But 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. He (Iago Aspas) is an interesting player, but he is at Liverpool. They have injuries as well, so that might not be possible. But we are looking at other options.
“A lot of clubs will do business and everyone needs players in certain positions. We just have to do our best and not talk about names.”
The Swans travel to Chelsea on Boxing Day for the first of three games in the space of six days.
Laudrup’s men recorded a famous victory at Stamford Bridge last January in the first leg of the Capital One Cup semi-final, en route to winning the club’s first major trophy.
But the Dane is anticipating a tough encounter against Jose Mourinho’s side, but hopes his players can draw on last season’s success.
“When you play Chelsea you know it will be a tough game,” he said. “It wasn’t so long ago that they won the Champions League, and they lifted the Europa League last year as well.
“I watched them against Arsenal on Monday night, and they had (Juan) Mata, (Samuel) Eto’o and David Luiz on the bench.
“A lot of these players could play against us on Boxing Day and we have to go there with confidence that we can do something because we’ve done it once before.”
Meanwhile, the Swans were handed a boost with the news that Ben Davies has signed a new four-and-a-half year contract at the club.
The defender sees his new deal run until the summer of 2017, and Laudrup was paid tribute to the youngster.
“He’s a very positive story,” he said. “Not just for us, but for Welsh football in general because it must be nice to see one of your own coming through.
“He came in and took his chance, and the rest is history. He is doing well, playing for national team, and is still young as well.
“You still feel he wants to improve, both in training and games, and that is the right attitude to have.”