That assessment was vindicated in style when Belle Plaisir , who she owns with Lance Hickman, won the Gr.3 RA Lee Stakes (1600m) at Morphettville in South Australia – possibly earning her a crack at Group One company.
Racing on the anniversary of her first black type victory, the Listed Rangitikei Gold Cup (1600m), the five-year-old shot through on the rail under an inspired ride from Barend Vorster to beat Cherry Tortoni and a field including the million-dollar earners Dalasan and Countofmontecristo, scoring her first Group race success for trainer Tony McEvoy.
"I remember saying to Lance when I first rode her that 'this horse is a Rolls Royce', and I kept calling her that nickname," Tanner said.
"People used to say to me 'how can you say that about a horse that hasn't even been to a trial', and I said 'you mark my words, this is going to be a very, very good horse'."
Tanner, who co-owns Belle Plaisir with Lance Hickman and who trained the mare at Awapuni prior to her move to Australia in September last year, said the mare would now head to Queensland for the A$500,000 Magic Millions National Classic (1600m), a fillies and mares weight-for-age race at Eagle Farm on June 4.
If she performs well and comes through the race in good order, she will return to Eagle Farm on June 25 for the Gr.1 Tattersall's Tiara (1400m), also run at weight-for-age for fillies and mares.
"Even though it was officially a Good4 on Saturday, she is better when she can get her toe in the ground, so given the amount of rain they have had in Queensland it should really suit her," Tanner said.
Tanner and Hickman were called by McEvoy shortly after Belle Plaisir won the Rangitikei Gold Cup to see if they were interested in letting him prepare her in Australia. Tanner and Hickman said they would not sell her, but they did lease a minority racing share to McEvoy's Kildalton Park Racing.
After the arrangement was made, Belle Plaisir wintered in New Zealand and then won a trial before heading to McEvoy in September. Once there, she ran well in three Victorian spring starts, including a fourth in the Gr.3 Hong Kong Jockey Club Stakes (1400m) at Flemington on Melbourne Cup Day.
This year, she won a mares race at Oakbank and finished fourth in the Gr.2 Queen of the South Stakes (1600m) at Morphettville prior to Saturday's win back at Morphettville.
"We were very happy at how she was but she had some challenges," Tanner said.
"She had a very bad draw, she wasn't well weighted up against the boys, there were horses in that race that had won $3.7 million (Dalasan) and others that had won more than $1 million, so with 53.5kg she was disadvantaged at the weights.
"She'd also never won on a Good 4 track before, she likes to get her toe into the ground. But Tony said the track had a good grass covering, and he always puts her welfare first – he's scratched her before if he thinks the track is too firm for her."
Once her Queensland campaign is over, Belle Plaisir is likely to winter in the warmth of Queensland prior to heading back to Melbourne for a spring campaign. Tanner said next season would be her last on the track.
The venture has encouraged Tanner to consider sending any other good horses they acquire to McEvoy, who she can't speak highly enough about.
"The communication, the audio clips, the video clips of the horse on a weekly basis … we're kept up to speed continually, so we never feel as though we've let her go or lost touch," she said.
"We get a call before the race, after the race, you're just really made to feel part of the team even though we haven't been able to go over due to Covid – though that will change for her next start because we're going to fly over for it."
Behind Belle Plaisir in third on Saturday was Excelida , who is owned by Cambridge Stud's Brendan and Jo Lindsay, who played an important part helping Tanner with Belle Plaisir's now two-year-old half-sister by Alamosa.
"Unfortunately Eden died giving birth to the filly, and Cambridge Stud very kindly loaned a mare and looked after the orphan foal for us," Tanner said."We were most grateful that people at that level would be so generous. It goes to show there's some really good people in racing."