Ritchie is reluctant to try it again because Zurella has to win either of her two next starts, the Naturalism Stakes or the Herbert Power Handicap, to grab a spot in the Caulfield Cup.
"While she's winning I don't want to tamper with the formula. She's pushing out, which we saw yesterday, and she's not racing like a horse that needs blinkers.
"If she starts to show she needs blinkers she'll get them very quickly."
It was a different Zurella who lined up on Saturday. She is much stronger than last season and even though winning jockey Craig Newitt thought she was a bit of a handful to mount, he found that once he was on her back and out on the track she behaved perfectly.
"She's much better now than last season, when she would just run over the top of you before a race," said Ritchie.
"She's matured in every aspect and she's not the fragile horse she was last season."
Southern Speed and her trainer Leon Macdonald have done all they can.
Now it's up to jockey Craig Williams to decide if he will ride the grand mare in her main spring mission - whatever it may be.
Southern Speed pulled out yet another super effort in the group two Makybe Diva Stakes (1600m), nosing out Manighar in a finish that had even her jockey fooled, reports AAP.
For Southern Speed, the result avenged her equally close second to Manighar in the Australian Cup last autumn.
But it also created a potential problem for Williams. Macdonald made it clear Williams had the ride on Southern Speed for as long as he wants it as she heads toward either the Caulfield Cup or the Cox Plate.
The trouble is Williams, who rode Southern Speed to victory in last year's Caulfield Cup, also has the option of riding Melbourne Cup winner Dunaden in this year's Caulfield feature and the champion 3-year-old Pierro in the Cox Plate.
Southern Speed ($4.20) hit the lead soon after straightening and pulled out all stops to beat Manighar ($3.30).
