Brooks Koepka hopes the weather can turn the tide in his favour at The Open after claiming he has "putted the worst in the entire field" at Royal Portrush.

The four-time major winner started the day just three shots back of overnight co-leaders Shane Lowry and J.B. Holmes and there were opportunities to score low on a calm day on the Dunluce Links.

Koepka did manage to shoot a 67, but squandered several opportunities to go even lower and will start Sunday seven shots back of Lowry after the Irishman dazzled with a 63.

While the world number one is happy with how he has struck the ball tee-to-green, his performance on the dancefloor has left him frustrated.

"Nobody has hit it better than me this week. I've hit it as good as I could possibly imagine. I putted the worst in the entire field," he said. "It's very frustrating, I'm disappointed.

"I need to figure out the putter. I just need to putt good one day. So I'm about to go do a whole bunch of work on that putting green and see if I can somehow find confidence, somehow find anything."

The forecasted adverse weather on Sunday has seen tee times brought forward and Koepka is not ready to give up his challenge just yet.

"I need it [the bad weather]. Being seven back. Here you need some wind, you need some rain. You need anything that can kind of go your way. And that's got to be an advantage," he added.

"Especially the way I'm striking the ball. I've struck it so good. If it's going to be windy, you need to be able to strike it good, control your flight, and figure out where you want the ball to end up."

Justin Rose, who played alongside Koepka, is also seven shots back of Lowry.

The 2013 U.S. Open winner is expecting the Irishman to cope well in the forecasted tough conditions, but like Koepka is hoping the weather can do him a favour.

"It [the weather] offers you a little bit more hope than if it was a benign day. Who knows what it might take, it might take 63," he said.

"I'm just projecting Shane is going to have a decent finish here, he's got a great short game, that will stand him in good stead on a tough weather day, he's Irish. If there is a tough-weather-day player, it probably is him. 

"It doesn't make it easy trying to win a major in conditions like that."