Vain Queen has kept her unbeaten record in tact with a first-up victory at Caulfield despite jockey Glen Boss declaring the talented mare raced well below her best.

The John Sadler-trained Vain Queen, the $2.15 favourite, made it four wins from as many starts with a three-quarter length success in the Sportingbet Sprint Series Heat 1 Handicap (1000m) but it could be the final time she is seen this spring carnival.

Malua Racing's Troy Corstens said the mare was only ever going to have a light campaign and Boss has recommended the four-year-old heads for a spell to wait for the autumn.

"She was well below her best today so I would be suggesting she goes to the paddock," Boss said.

"She's a very good filly, she's going to be very valuable in the autumn so I think connections will take the conservative route.

"I'll tell you what she is though, she's a winner."

Vain Queen settled third in the run but was forced to chase before the home turn and appeared to be under pressure as they straightened for home.

Despite doing plenty wrong in the straight Vain Queen was able to get home in front of the fast-finishing Serene Star ($11) with leader Holder Sunset ($26) clinging on for third, another 1-1/4 lengths away.