While defenders Karl Amon and Jarman Impey could return from injury, the Hawks are being conservative with Watson and have ruled the star out for another week.
Watson missed last weekend's bad loss to Melbourne with a minor hamstring injury, but coach Sam Mitchell had been optimistic that he would return to face the Blues.
"On Tuesday he ran 88 per cent of his top speed, which is still faster than most of us," Mitchell said before Thursday morning training.
"But just from a confidence point of view, we don't feel like it's worth the risk with him - so he'll miss one more and he'll be available for next week."
Nash has not played since round 10 because of a disc-related injury in his neck, affecting strength and power down one of his arms.
"It's pretty complicated ... its quite unusual, so we've had to go to some experts - he went to Sydney through the week and got some further treatment," Mitchell said.
"Now, he definitely won't play for a month ... but we have no timeline, so realistically he could miss the rest of this season.
"He's very frustrated. Nashy's rundown to me is we've sort of gotten to the bottom of what's happening and now it's about how to fix it."
Asked if Nash would recover from this injury, Mitchell was adamant that it is "when, not if".
"The worst-case scenario is he misses the rest of this season."
Defender Josh Battle is recovering from having his appendix removed last week and also will remain sidelined.
"The boys are all saying he has man flu and he should be fine, but unfortunately he won't be available either," Mitchell said.
Midfielder Ollie Greeves, 19, will be Hawthorn's seventh debutant this season. He was recruited late last year through the rookie draft.
Defenders Jarman Impey (hamstring) and Karl Amon (knee) will return from injury and the Hawks left out Jack Dalton, Flynn Perez and Bodie Ryan.
The Hawks fell 96 points behind against the Demons last weekend, before restricting the damage to 35.
Mitchell said effort, not missing players, was the issue. He also noted the team showed character by rallying late.
"When you give behaviours like that, you get performances like that," he said.
"I think of it as an outlier from an effort point of view. I don't think Hawthorn fans go to games and don't see effort from us."
Carlton have won seven straight under interim coach Josh Fraser and Mitchell is eager to burst their bubble.
"We've consistently spoken about making sure that we're a side that can compete consistently and we weren't able to do it. So we'll right that wrong this week," he said.
"They're obviously in great form and Saturday night at the MCG, what better way to try and bring them back down."
5°C