The Fillies' Mile turned out to be one of the best trials for the 1,000 Guineas last season. Shale can win the 2020 renewal at Newmarket on Friday (15.35 GMT) and shorten in the betting for the Classic on the same track next May. 

The 9/4 favourite Quadrilateral won the race 12 months ago when Love finished third. Those placings were reversed in the 1,000 Guineas and Love also won the Oaks. She is the best three-year-old filly over one mile to one mile four furlongs in training in the UK and Ireland. 

Love was withdrawn from the Arc because of concerns about the very soft ground at Longchamp.  Even so, the Fillies' Mile in 2019 was an excellent form guide for major races for fillies this season.    

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The runner-up, Powerful Breeze, has not raced again.  However, Cayenne Pepper who finished fourth, won a Group 2 contest for fillies and mares at the Curragh last month.

The top three in the betting for this week's race are also currently the top three in the betting for the 1,000 Guineas. The Group 1 will probably identify the winter favourite for the fillies' Classic over the same course and distance back at Newmarket in the spring. 

Shale is trained by Donnacha O'Brien while the third favourite, Pretty Gorgeous, is in the hands of his brother, Joseph.  Their Dad, Aidan, has two entries which is good news for the three stables. 

Horses trained by members of the family did not run at Longchamp last weekend because of contaminated feed.  Pretty Gorgeous missed her race so has been rerouted to Newmarket. The O'Brien's account for four of the 11 declarations for the Fillies' Mile.

Indigo Girl is the second favourite for this race and the 1,000 Guineas. The John Gosden representative has won two races from two starts during her juvenile season.  The win over Dubai Fountain at Doncaster last month was in a Group 2 race and on ratings Indigo Girl has something to find with Shale and Pretty Gorgeous. 

These two fillies have met three times this season, in progressively better races.  Shale came out on top in the Group 1 and Group 3 meetings while Pretty Gorgeous prevailed in the Group 2 clash. In terms of overall margins of victory Pretty Gorgeous is a quarter of a length in front. 

However, both horses earned their best career Official Rating in their most recent start, the Group 1 Moyglare Stud Stakes over seven furlongs at the Curragh last month.  Shale won the race while Pretty Gorgeous finished second, three quarters of a length in arrears carrying the same weight. 

Snowfall and Mother Earth, trained by Aidan, were unplaced and neither of these runners is likely to reverse the form with the two market leaders, trained by his sons. Isabella Giles has the ratings to make the frame alongside Indigo Girl. 

These UK-trained fillies are probably running for third place because Shale and Pretty Gorgeous have achieved more on the track and are progressive. The combined price for the O'Brien siblings to train the winner of the Fillies' Mile is about 11/10 so its 4/6 the field which includes the two unfancied O'Brien senior entries.

Dubai Fountain could feasibly reverse the Doncaster form with Indigo Girl and looks a generous each way price at 16/1 with bet365. The margin of defeat was only three quarters of a length and Dubai Fountain was carried left inside the final furlong so was an unlucky loser. Third-placed Zabeel Queen was well beaten so winning the Fillies' Mile looks beyond her. 

The major form races suggest its Shale and Pretty Gorgeous for the forecast. Based on the comparative ratings Shale is marginally preferred for the Fillies' Mile and then the 1,000 Guineas.