"It comes down to whether she can run two miles and whether she's good enough."
Lees thinks there have been enough pointers to suggest Lucia Valentina, winner of the Vinery Stud Stakes and Turnbull Stakes at Group One level, can cope with the Melbourne Cup distance.
"She's got the profile to do it," Lees said.
"I don't know if she's got the pedigree to do it but she's got the profile to do it.
"The way she relaxes and she has been strong through the line at every distance she has run over. She's just got to go the extra half a mile."
Lees has taken heart from the way Lucia Valentina finished off in the Caulfield Cup.
"She had a bit of adversity and still had the quickest last 200 metres," he said.
Lucia Valentina is equal second favourite at $7 with German galloper Protectionist who hit the line well for fourth under a big weight in the Herbert Power Stakes.
Admire Rakti, the $4 Melbourne Cup favourite, impressed at Caulfield under topweight of 58kg after travelling three-wide.
The win earned Admire Rakti a 0.5kg penalty for the Melbourne Cup.
"I thought he might have got more. But still 58.5 [kilograms] at the end of two miles can tell," Lees said.