Captain John Terry is out of Chelsea's Premier League clash with Wigan on Saturday after suffering inflammation in his knee.
"John Terry has an inflammation with his knee," manager Rafael Benitez said. "A set-back, but not serious. He will not be available for tomorrow."
Terry has only just recovered from a knee injury caused when he slipped and crashed into Liverpool's Luis Suarez on Nov. 11. After missing the Club World Cup, Terry returned to action Jan. 12, but has now suffered an inflamation which will keep him out for the weekend.
Goalkeeper Petr Cech (finger) and Demba Ba (broken nose) are expected to be fit, with the striker in line to play with a protective face mask, while Eden Hazard is available again after serving his three-match ban for his dismissal in the Capital One Cup semifinal second leg at Swansea.
Ba is ineligible for the Europa League trip to Prague, meaning he could play against Wigan, with Fernando Torres, who was not on international duty with Spain this week, saved for Europe.
"The positive news today, apart from the international break, is that we have David Luiz and Hazard coming back," Benitez added. "We have two more bodies, and that's really important. Mikel and Moses are still at the African Cup of Nations, in the final, but I'm pleased to have more players and more options."
Chelsea has three wins from its past 10 matches and is without a victory in four, with the latest slip coming in a 3-2 defeat against Newcastle last weekend.
It is hard to tell whether owner Roman Abramovich is losing patience with Benitez, who replaced Roberto Di Matteo in November, but never in his 10-year tenure has the Russian had three managers in the same campaign.
The Blues would slip to fourth ahead of kickoff against Wigan if Tottenham beats Newcastle in Saturday's lunchtime match.
"We know the problems and we are working on the solutions," said Benitez, when asked if he expected to see out his short-term deal until the end of the season. "The main thing is that you can score two goals, and then you are 2-0 up at halftime, then you have to finish the games."
Ashley Cole won his 100th international cap on Wednesday as England beat Brazil 2-1, with Chelsea teammate Frank Lampard scoring the decisive goal. Benitez was impressed with Lampard but unable to shed any fresh light on the midfielder's future.
"England did well, Lampard did really well scoring the goal," Benitez said. "I don't try to avoid the issue. I was very clear in the past and I will be very clear now and in the future: Frank is doing a great job for us, he's scoring goals, he's playing well, he's a good professional, he's very working hard."
Provisional squad: Cech, Turnbull, Azpilicueta, Ferreira, Luiz, Ivanovic, Cahill, Cole, Bertrand, Lampard, Ramires, Mata, Oscar, Hazard, Marin, Benayoun, Torres, Ba, Ake, Hilario.
Information from Press Association was used in this report.