A stomach bug has ripped through Australia's cricketers, including captain Steve Smith, but coach Darren Lehmann insists it's nothing too debilitating.
Pat Cummins was hampered by a stomach issue on day two of the MCG match, feeling so unwell he slept through the tea break.
Cummins' health improved on day three but Smith contracted the same illness overnight.
The captain scampered off the ground early in Thursday's morning session, with David Warner leading the side and organising fielders during Cummins' first over of the day.
Smith returned to the field at the end of that over and remained on the park throughout the day.
However, he remained unwell and uncharacteristically put down a catch at square leg when Alastair Cook was on 153.
"They've all been whingeing," Lehmann said.
"Theyll be fine. They're playing cricket for their country.
"It's a little bit of a tummy bug and most of them will be fine."
Smith, usually the safest set of hands in the team, also offered a Cook a reprieve when the opener was on 66 during day two. Cook will resume on 244.
"They were tough low catches and you have to stand so close at the MCG. That's not an excuse. We still expect to take them," Lehmann said.
"Steve sets a high standard in the slips ... he's been pretty good until this game."
Smith tried to pluck Thursday's low catch with one hand but the ball bounced out.
Cummins managed 11 overs on day two but struggled to generate his trademark express pace and bounce, regularly ducking off the field and at one point doubling over in the deep.
Cummins enjoyed a more productive start to day three, removing Joe Root with a pinpoint bouncer, but Cook helped England take complete control of the contest.