The three-time White Robe Lodge Handicap winner was galloped on early in the running of the group 1 weight-for-age classic at Otaki last month.
Trainer Claire Anderton suspects it happened as the pace eased a few hundred metres after the start of the 1600m.
‘‘I just think when there was that bit of argy-bargy going on,'' Anderton said.
‘‘She got herself in to a nice place, but when they've eased up, she's just gone sideways and something's got her.
Anderton exercised caution with the injury, as it was ‘‘in a bad place''.
‘‘It was on the joint of her hind leg.''However, the 6yr-old travelled well back to Wingatui after her unplaced run at Otaki, and has kept up to the mark nicely in work since.‘‘She's super in herself. She hasn't lost any weight and she's looking good,'' Anderton said.
‘‘She seems all right so we're aiming for the Valachi.''
The Diamond One has competed in the South Island autumn mares' feature once before, finishing fourth behind Emerald Queen in 2014.
The 1600m group 3 is run under set weights and penalty conditions.
Tommy Tucker, who finished 10th in the Otaki feature, is also Riccarton-bound although a fortnight later than The Diamond One.
‘‘He's going to Christchurch for the mile coming up there,'' co-trainer Brian Anderton said.
‘‘He'll probably back up then in the weight-for-age.''
The ‘‘mile'' is the listed Easter Cup over 1600m on April 16 and the Canterbury Gold Cup is a week later over 2000m.
Tommy Tucker will go slightly fresh in to the Easter Cup, a tactic which has worked well this season. In fact, his worst result this season - the 10th at Otaki - was 21 days after his flying second in the White Robe Lodge Handicap at Wingatui and was the shortest gap between his races for the 7yr-old this season.
‘‘We'll be able to get a jumpout or something in to him. But it won't be hard to keep him right.''
Anderton said the gelding had a week at part-owner Ian Nichol's farm and came back looking ‘‘nice and bright''.
Anderton confirmed both Blue ‘N' Gold (seven wins, $77,700) and Norah (six wins, $79,625) have been retired, while Ruby's Rose (four wins, $36,052) is likely to have her last start at Wingatui on Monday. All three mares are by White Robe Lodge sire Gallant Guru.
‘‘The three of them have done a good job.''
