A milestone birthday has been celebrated in typical Chris Waller fashion - with a winner.

Fittingly, it was delivered by Jim Cassidy who has enjoyed a successful partnership with the trainer, combining with Waller for his 100th Group One win on Zoustar during the spring.

Waller turned 40 on Wednesday and while he started the day with two seconds, a victory by Cassidy aboard Clever Boy in the fifth race ensured he didn't leave the track empty-handed.

"It's been a good day so far, I hope it continues," Waller said.

Sydney's benchmark trainer was planning a quiet celebration at home with his family ahead of a busy weekend in which he has Group One runners in Sydney and Melbourne.

The Canterbury meeting was interrupted when a storm hit after the sixth race, delaying the final event by 10 minutes and resulting in a track downgrade to slow.

There was also an important barrier trial after the last, rescheduled from Tuesday's session after jockeys became concerned about the Rosehill track.

The heat was won by $2.4 million David Hayes-trained colt Wilderness who scored by 1-1/4 lengths over Invinzabeel with that pair streeting their rivals by five lengths.

"He only does what he has to do. He's very laid back and has a lot to learn but he's a very nice horse," jockey Christian Reith said.

"He's ready to go to the races."

Reith was straight on the phone to Hayes after the trial but was unsure where Wilderness would make his debut.

The youngster is entered for the Black Opal Stakes at Canberra on Sunday but the Skyline Stakes on Saturday week appears the most likely option.

"He's trying to get me on it, that's all I have to worry about," Reith said.