Everything about the timing for Saturday’s Serena’s Song Stakes at Monmouth Park turned out to be fortuitous for jockey Luis Rivera, Jr.

Originally without a mount for the $100,000 feature race, Rivera was a late replacement on the Chad Brown-trained Lost Horizon just two races prior, after jockey Samuel Marin took off his mounts due to general soreness following a training mishap at Delaware Park earlier in the day.

Given that chance, Rivera made the most of it, waiting patiently for an opening along the rail entering the final turn. Once clear, Lost Horizon took it from there, coasting to an 8½-lemgth victory for her first career stakes win.

Domino Vitali, the 9-5 favorite and pace-setter for the opening seven-eighths of a mile, held second by a neck over Ourdaydreaminggirl.

The winning time for the mile and 70 yards was 1:42.88.

Lost Horizon returned $8.20 to win.

“I found out they wanted me to ride this horse around the third race when Samuel Marin took off his mounts. It’s my first time ever riding for Chad Brown so it means a lot,” said Rivera. “I had plenty of horse the whole way so I was just trying to save ground. I knew I had enough horse to make my move whenever I wanted to so I wasn’t concerned about keeping her in the clear because I knew when I asked her that no one was going to stay with her.

“I was just waiting for the rail and watching (Domino Vitali) because I didn’t know if that horse would drop down on me. So I was waiting until the timing was right and then the rail opened for me and she just took off.”

A Kentucky-bred daughter of Wow Cat, Lost Horizon was unraced at 2 and had a pair of solid – but non-winning efforts – in her only starts at 3.

She has flourished as a 4-year-old with three wins and a third from her four starts.

“This filly is impressive when you look at her,” said Luis Cabrera, who oversees Brown’s division at Monmouth Park. “I think she likes the distance, too. She wants to go long. She’s more mature now, more experienced. Some horses take a little while to put it together.

“She’s a big, big filly. She just needed time. That’s why she didn’t race at 2. She just needed time because of her size. Those bigger horses take time. The way she looks and the way she was training I had a feeling she would run big. I had her in Florida and she was doing well. You could see the maturity.”

Brown has now won both stakes contested at Monmouth Park this season, taking the Long Branch Stakes last weekend with Hedge Ration.

Rivera, meanwhile, riding full-time at Monmouth Park for the first time since he was an apprentice in 2023, won four races on the eight-race card.

He was content to sit early through fractions of :23.34, :47.28 and 1:12.17 for six furlongs before moving inside and waiting for rail clearance coming out of the final turn.

“He gave her the best ride possible,” said Cabrera. “He rode her great. He saved all the ground and then found that opening along the rail for her to take off.”

Marin, meanwhile, was sent to Monmouth Medical Center for X-rays complaining of general soreness, according to track physician Dr. Angelo Chinnici.