For trainer John McNair, looking back on the past decade is a reflection on the career of grand sprinter Mustard.

The 12-year-old lines up for his 101st start at Rosehill on Saturday almost 10 years after his first appearance in June 2000.

Mustard's 100th race produced a fairytale victory at Randwick and although mindful it must end soon, McNair says the gelding retains a zest for racing.

"His mental attitude is the thing that keeps him going," McNair said.

"He is positive and he loves winning and he must love what he's doing to keep doing it.

"He's a happy horse and sounder now than he was three years ago.

"It's amazing to think he has been racing for 10 years."

Mustard will run in the Green Day At The Gardens Handicap (1500m) with Rodney Quinn again on board.

He has drawn barrier one in a classy field with McNair's main concern the pace of the race.

"I am concerned about the lack of any obvious pace in the race," he said.

"He needs a genuine speed on but barrier one gives us some options."

McNair admitted the publicity surrounding Mustard's 100th start brought with it pressure that the gelding should not be racing.

"There was pressure before his last start but one thing I know is that he will always have a home here with us," he said.

"It took him a bit longer to get over his last run than it used to but that's to be expected.

"But he came home from the races and was so proud of himself.

"If he didn't want to do it, he wouldn't."

McNair credits the recently-introduced Benchmark system with prolonging Mustard's career.

"It's the greatest innovation in my time in racing," he said.

"He was getting weighted out of races but this system means he can come down in the weights.

"Virtually you are handicapping your own horses.

"But if he wins another race he will probably be handicapped out of these sorts of races so if that happens I probably will retire him."

His record from his 100 starts is 16 wins and 23 placings with his most recent victory taking his earnings past $700,000.

Mustard started at $26 at Randwick but was an $8.50 chance for Rosehill with TAB Sportsbet on Thursday.

The John O'Shea-trained Informality, who finished third to him last time out, was the $3.20 favourite.

© AAP 2010 Published 31/12/09