Chelsea defender David Luiz may miss the crucial Champions League quarter-final second leg clash with Benfica on Wednesday after he sustained an ankle injury against Aston Villa.
The Brazil international was forced off at half-time during the 4-2 victory at Villa Park, and was replaced by January acquisition Gary Cahill.
Chelsea have been unable to assess the full extent of the damage so far, and the 24-year-old's prognosis is likely to be revealed over the next day or two.
"We'll have to wait for 48 hours to asses David Luiz," interim Chelsea manager Di Matteo told BBC Sport after the match.
He added: "He felt his ankle ligaments and came off."
Having been derided for his unpredictable performances earlier this season, Luiz has grown in stature in more recent weeks, forming a solid partnership with Chelsea captain John Terry.
Luiz was particularly impressive in Chelsea's most recent Champions League encounters - with Napoli and Benfica - and his potential absence at Stamford Bridge this week will come as a blow to Di Matteo.