Eden Hazard missed Chelsea's open training session ahead of Tuesday's UEFA Champions League semi-final first-leg at Atletico Madrid.
The Belgium midfielder has been sidelined since suffering a calf injury in the second-leg of the quarter-final win over Paris Saint-Germain, but Chelsea are hopeful he will recover in time for the trip to the Vicente Calderon Stadium.
His absence from the session at Chelsea's training ground will only increase concerns that Hazard might lose his fitness race, though he did travel with the squad.
When asked about Hazard on Friday, assistant coach Steve Holland admitted he could be running out of time.
"To be considered, he obviously needs to train with the group very quickly," said Holland. "It's a day-by-day one at the moment."
Manager Jose Mourinho must find a way to inject fresh life into his side after Saturday's lacklustre 2-1 defeat by Sunderland dealt a major blow to their Premier League title chances.
Striker Samuel Eto'o will be absent with a knee injury. Goalkeeper Petr Cech missed the match at Stamford Bridge through illness, but trained as normal, while David Luiz and Andre Schurrle could return after starting on the bench.
Fernando Torres has fallen out of favour in recent weeks, but Mourinho might consider recalling the Spaniard for the return to his former club.
Branislav Ivanovic is suspended, meaning Cesar Azpilicueta could be switched
from left-back to right-back, freeing up a possible place for Ashley Cole.
Nemanja Matic and Mohamed Salah are ineligible, having played for Benfica and Basle, respectively, earlier in the competition.