Jason Day isn't persuading himself to think about winning his second major title quite yet but admits the adrenaline is flowing again at the prospect of battling at the sharp end of the British Open.

He hasn't enjoyed a top-10 finish in a major for three years but the rejuvenated Australian is lying joint-fourth at halfway at Hoylake, in the ideal position to pounce if the runaway leader by five strokes, American Brian Harman, falters.

Of all the players on view on Friday afternoon in pursuit of Harman, none was more convincing than the 35-year-old Queenslander, who made two birdies on the final tough four-hole stretch on his way to a four-under 67.

"I'm not really focused on trying to win the tournament right now. I'm just trying to cut into his lead, whereas he's trying to keep that lead. That's a little bit of a different mindset," said Day.

"I'm just trying to stay in my own little world and hopefully tomorrow I'm a little bit closer.

"I'm excited about it because, even though I've played great for the most part of the year, I haven't played the majors well this year, and it's been a little bit disappointing," added Day, who after years of major back problems showed signs of the form that once made him the world No.1 as he won his first PGA Tour event for five years in May.

But Day finished tied for 39th at the Masters and missed the cut at both the PGA and US Open. "But this week could definitely change it," said Day, who has a pretty poor record at the British Open except for his serious run at the title in 2015 when he finished just a shot outside making the three-man play-off.

"T4 (tied for fourth) right now is great. I've got a number in my head that I need to win with but I'm not going to say it because, typically, when I say it, I'm terribly wrong," smiled Day.