Pacer Mitchell Starc also hit in the knee during batting practice
Australian all-rounder Shane Watson was forced to cut short his training session in the Melbourne Cricket Ground nets after being hit on the helmet by a bouncer on Tuesday, three days before the start of the third Test against India.
Watson, under pressure for his place at number three in the batting order, was knocked to the ground when a short ball from James Pattinson hit him flush on the helmet.
"Shane Watson shaken up, but OK, after helmet blow," Cricket Australia tweeted.
Pattinson was also shaken up by the incident, which came less than a month after former Australia batsman Phillip Hughes was killed by injuries sustained when he was hit by a short ball in a domestic match in Sydney.
Left-arm paceman Mitchell Starc also left the session early after being hit on the knee by a ball but his likely replacement in the side, Ryan Harris, was apparently untroubled by the thigh injury that ruled him out of the second Test.
The hosts, who take a 2-0 lead into the Boxing Day Test, already had injury concerns over David Warner, who skipped the session to nurse a thumb injury he sustained on the final day of the four-wicket victory in Brisbane on Saturday.
The aggressive opener, one of Australia's best performers with the bat this year, had little doubt in his own mind that he would be ready to go by Friday.
"I will definitely be playing, I will be doing everything I can," he told reporters when the team arrived in Melbourne on Monday.
"Obviously it's a bit painful, it's the one I broke before, but I'm not missing a Boxing Day Test, that's for sure."
Uncapped batsman Joe Burns was brought into the squad on Sunday to cover for injured all-rounder Mitchell Marsh, while captain Michael Clarke will miss the rest of the series after surgery on a hamstring problem.
