Jason Day says holding his nerve will be the key to winning the Deutsche Bank Championship on Monday.

The 22-year-old holds a one-shot lead from American Brandt Snedeker heading into the final round but admits playing it safe would only end in disaster.

Day became the youngest Australian to win on the PGA Tour when he claimed the HP Byron Nelson Championship earlier this year, but he has also been in winning positions in at least two other tournaments and not finished the job.

Should Day claim victory on the Labour Day holiday in America, he would become one of just six two-time winners on Tour this year, including Ernie Els, Steve Stricker, Justin Rose, Jim Furyk and Hunter Mahan.

Day said the biggest battle in the final round will be the mental one - and he hopes he can remain calm under pressure.

"I need to try and give myself as much birdie chances out there as possible. I think that's the key tomorrow. It's going to be gusty tomorrow, and patience is probably going to be the biggest key, as well," he said.

"I think the biggest thing for me tomorrow is to commit to the shot that needs to be hit and not standing up there and second-guessing myself and not committing to a shot because the moment I do that, the moment the ball starts to go a little wide, especially with the driver," he said.

Day's lead could have been much more had Snedeker not stolen his thunder on the final hole in Sunday's third round.

Day was level with the American and holed a birdie on the 18th, but Snedeker's chip for par means the Australian holds just a single stroke advantage going into Monday's final round.

"Thinking in my head, I was thinking that he was going to just get up-and-down and make bogey, and I was going to make an eagle or birdie the hole. That would have gave me a nice little cushion going into tomorrow," he said.

"But Brandt is a competitor, and he stuck it out until the end and made a really good par save there. I'm going to look forward to tomorrow. It's going to be really, really enjoyable."