Donnie has won five caps in a row but fears he could still be sent down to sit among the replacements for Saturday's revenge clash with Australia at Hampden.
But Donnie is convinced his uncertainty about a starting slot is a positive for the team.
Donnie told the Daily Record: "For ages, Australia have had fierce competition for back-row places and that has made them such a potent unit.
"Now we are working our way into a similar position and the more jostling there is for jerseys, the stronger we will be.
"We have Jon Petrie performing superbly alongside me as skipper of Glasgow and Jason White will be desperate to show he is far too good to be a bench player.
"The fact that Jason was among the substitutes against Japan is just an indicator of how well we are served in the breakaway department.The more headaches we can give the selectors, the better!"
Donnie is confident Scotland will be better equipped to match the Aussies this time compared to what happened at Murrayfield a fortnight earlier.
He said: "Obviously we have gone into all our matches against them believing we could win.
"Things have not gone to plan - but every time we face them we learn more and more, not just about Australia, but also about ourselves.
"I certainly feel more confident because I am two caps more experienced and have a better understanding of the Scotland squad systems.
"We can do something special on Saturday, and despite being born in Edinburgh it would be fantastic to do it in Glasgow.
"I am not a huge football fan but realise the significance of playing at Hampden. I've never been there but I am really looking forward to it.
"What will make it extra special is that my mum and dad will be among the crowd. They missed my first three Scotland appearances because they couldn't get out to Australia.
"Then, when we faced the Wallabies at Murrayfield, it was their turn to be abroad. They made it to Perth last week and seeing them at Hampden will give mean extra buzz."