Australia batsman Usman Khawaja limped off with a suspected knee injury during day one of the fifth Ashes Test at the SCG.
Khawaja, who is under pressure to keep his place, got his knee caught in the outfield while fielding during the final session on Thursday.
The left-handed batsman tried to slide to field a Dawid Malan drive but instead saw his knee jar before he limped off.
England were 160-3 at the time with Malan (28) and captain Joe Root (42) at the crease.
Khawaja returned to the field four overs later.