Dettori, who has ridden more Group One winners this season than in any other, will be aiming to win the big handicap for just the second time, having broken his duck in 2011 on Jamie Osborne's Never Can Tell.
Mullins was successful 12 months ago with Low Sun and he could also run Stratum and Great White Shark.
Dettori's agent Ray Cochrane said: "I'm hoping Frankie's on, I'm just waiting for Willie to confirm.
"Ryan (Moore) usually rides for Willie, but Aidan O'Brien has four in there and you'd think he's certain to have one.
"Frankie looks to have a good book (of rides) on Saturday, so I just hope there's no more rain."
Dettori and Mullins famously combined to win the Irish St Leger in 2016 with Wicklow Brave, while the Italian was on board when the Closutton trainer's Max Dynamite went within half a length of landing the Melbourne Cup in 2015.
Alan King intends to run all three of his entries, with Who Dares Wins set to head the weights.
The versatile seven-year-old arguably produced a career-best effort last weekend in France when fourth in the Group One Prix du Cadran.
With a novice chase campaign in the offing, King has been tempted into one more run on the Flat, should all go well for the rest of the week.
He will be joined by useful stable companions Rainbow Dreamer and Couer De Lion.
"As long as I'm happy with him Who Dares Wins will run on Saturday," said King.
"It was a very good run in France, I was pleased, and they've put him up another 5lb so technically he's well-in.
"The other two will run as well providing they work well enough (on Wednesday)."
Who Dares Wins won the Northumberland Plate in June narrowly from Dubawi Fifty, but the latter has been unplaced twice since then.
However, his trainer Karen McLintock believes he has valid excuses for Goodwood and York, and is hoping for a better run.
"When Frankie came back in after York he was it was a stupid race and he didn't get a good enough early position," said McLintock.
"We know he's good enough given his Plate form and he's been dropped a few pounds. Good to soft ground would be ideal for him.
"We've booked Adam Kirby, so we're hoping for a good run - he's in good form at home."
