Swansea's Michu is likely to miss the next two games after twisting his ankle in the 1-0 defeat by Cardiff, Swans boss Michael Laudrup has revealed.
Swansea face Russia's Kuban Krasnodar in the Europa League and Stoke in the league before an international break.
The Danish manager said: "Michu is not 100% right now, he is struggling with some physical problems.
"He had to leave the pitch with another twisted ankle, so probably he will be out for a couple of games."
Spanish striker Michu was subdued after missing an early volley at the Cardiff City Stadium and was replaced in the second half after going over on his ankle.
The defeat for Swansea meant that their south Wales rivals moved above them in the Premier League with Laudrup's side slipping to 13th in the table.
But the manager said his team were not outclassed after Cardiff defender Steven Caulker scored with a header from a corner before Swans goalkeeper Michel Vorm was sent off for a late challenge on Fraizer Campbell.
Laudrup told BBC Sport: "It ended up being disappointing, it is always that way when you lose a derby and we really wanted to win.
"Our plan in the first half was to control it and we did that quite well, we kept them away from any chances. When we wanted to bring on some players to go for the game, they scored from a set piece. We knew that they were strong from these and it's one of the only chances they had from the game.
"It's the first [set-piece] we have conceded from this season, apart from a penalty, but that is different."
Vorm's red card came in stoppage time, and because Swansea had already made three substitutions, Angel Rangel had to spend five minutes in goal, going on to save Peter Whittingham's free-kick.
Laudrup had few complaints about the sending off, saying: "He was the last man, everything happens so quickly. From the outside it seemed like he was the last man so it seems like it was OK. The referees need to take that decision in a split second so that's what can happen."