Glen Boss believes a soft track is the key to extending his outstanding record in the Doncaster Mile to six aboard the David Hayes-trained Largo Lad at Randwick on Saturday.Boss doesn't rate the Encosta De Lago as highly as the first four of his five Doncaster winners but gives him a good hope in the tough 1600m event with the sting out of the ground, which he loves."Sprint By, Private Steer, Racing To Win and Haradasun were serious Group One horses and you couldn't really rate him up with them.

Glen Boss believes a soft track is the key to extending his outstanding record in the Doncaster Mile to six aboard the David Hayes-trained Largo Lad at Randwick on Saturday.

Boss doesn't rate the Encosta De Lago as highly as the first four of his five Doncaster winners but gives him a good hope in the tough 1600m event with the sting out of the ground, which he loves.

"Sprint By, Private Steer, Racing To Win and Haradasun were serious Group One horses and you couldn't really rate him up with them. He's not quite there yet," Boss said.

Largo Lad drew well in barrier five in the $2 million feature but Boss said it didn't really matter where he drew as he will get back and finish on strongly.

"He will get back and run on. He is such a big horse he looks like he can't sprint because he has such a big stride, but he actually has a very good sprint," he said.

"The conditions should suit him and give him his chance."

The jockey won his first Doncaster aboard the Gai Waterhouse-trained Sprint By in 1996 and has won the race four of the last five years on Private Steer (2004) for John O'Shea, Racing To Win (2006) for O'Shea again, Haradasun (2007) for Tony Vasil and Triple Honour in 2008 for Chris Waller.

"You need the best handicapped horse to win the Doncaster," Boss said.

"You don't generally get slowly-run Doncasters. It's usually a pretty tough race and this year Sir Slick should ensure they run along."

Largo Lad began his career with Wangaratta trainer John Ledger and won two races, a Bendigo 1400m maiden and a Moonee Valley 1600m three-year-old race, from his first seven starts.

After he finished eighth to Weekend Hussler in the 2008 Randwick Guineas (1600m), owner Jim Racovolis sold the gelding to Hayes, Peter Devitt, Les Gordon and Boss' friend Scott Perrin and his wife Rachel.

He had his first run for Hayes when fourth to Dealer Principal in the 2008 Rosehill Guineas (2000m) and was spelled after finishing 15th to Nom Du Jeu in the AJC Australian Derby (2400m) at Randwick.

He has since won three races, over 1400m on a heavy track at Sandown, a 1200m sprint at Flemington and the Group Two Blamey Stakes (1600m) at Flemington.

That was his big test to see if he was up to the Doncaster and he passed it with flying colours under 54kg.

The stable's confidence grew even more when he ran on nicely from last for a 2-3/4 length sixth to Vision And Power in the George Ryder Stakes (1500m) in heavy going at Rosehill last start.

"He ran the fastest 400 metres of the day," Boss said.

Largo Lad, who will carry 51.5kg, is at $13 on TAB Sportsbet with Emirates Stakes winner All Silent the $5.50 favourite.

But Boss rates triple Group One winner Theseo ($11) as the testing material.

"I don't think coming back from the 2400 metres of The BMW will worry him," he said.

"He's a class horse."