Swansea striker Wilfried Bony will be sidelined for "several weeks" after suffering a hamstring injury in the Europa League defeat to Valencia.
Bony limped off just before half-time in the 1-0 Group A loss, having pulled up clutching the back of his right leg chasing a long ball.
With Michu also currently sidelined, due to an ankle problem, the injury comes at a less than ideal time with a daunting trip to Manchester City lying ahead for Michael Laudrup's men on Sunday.
The Swansea boss said: "It could be quite a serious one. We'll have to wait two or three days until we get a scan but unfortunately we are talking several weeks.
"It is a blow but that's how it is. You have to accept it and when you have a lot of games this is a possibility.
"Let's see what happens with Michu in the next week or so."
Swansea also lost right-back Angel Rangel with a calf problem, but Laudrup does not believe his injury is as serious as Bony's.