Now Shane Watson has done all he can to show he's ready for the Test series decider against South Africa, it's up to selectors.
Watson has overcome a calf injury and moved well as he bowled five overs on Thursday, the allrounder's final fitness test before the third Test starts on Saturday in Cape Town.
Selectors are yet to declare their intent, but Watson shapes as a likely inclusion given the side's batting woes and overworked bowlers in the second-Test loss in Port Elizabeth.
The 32-year-old, told he needs to bowl to warrant national selection during a four-week lay-off with a calf injury, would bring much-needed respite to Harris, Mitchell Johnson and Peter Siddle.
The trio bowled a combined 133 overs in the second Test - the highest mark in a Test for three Australian pacemen in three years.
"Having Watto back would be huge, having that extra bowler," Harris said.
"We've seen when Davey (Warner) has to bowl a few here and there and Michael (Clarke) has to fill in - they're bowling Watto's overs."
Watson is tipped to be drafted into the side at the expense of either Shaun Marsh or Alex Doolan.
"Who he comes in for I don't know. The guys who are already in there, Doolan and Marsh, didn't go well last game but have done well," Harris said.
"But I think we need Watto playing. It's just a matter of who he comes in for."
Marsh and Doolan both made runs in Australia's first-Test win before floundering in Port Elizabeth.
Coach Darren Lehmann has said it would be "really unlucky" for batsmen in the side to be dropped, but conceded Watson's overs added another dimension to his team.
"As long as he's bowling overs and he's fit, we would love to have that extra bowler," Lehmann said after his side slumped up a 231-run loss.
Watson has form at Newlands, having taken 5-15 from five overs in 2011.
Michael Clarke joked that if national selectors were to drop a batsman on form to make way for Watson, it might be him.
Clarke has gone 11 Test innings without a score of substance and was hard at work on Wednesday, spending a day off in the nets at Newlands taking advice from coaches Darren Lehmann and Michael Di Venuto instead of sightseeing.