World No. 10 Jason Day did not let vertigo slow him down at the 2015 U.S. Open and is now in a four-way tie on top of the leaderboard with Jordan Spieth, Dustin Johnson and Branden Grace.

Before tying for the top spot, Day was even unsure if he could participate Saturday after collapsing as he was about to close his second round Friday.

"I didn't feel that great coming out early and then felt like -- I felt pretty groggy on the front nine just from the drugs that I had in my system, then kind of flushed that out on the back nine," Day said according to ESPN.

"But then it kind of came back. The vertigo came back a little bit on the 13th tee box, and then felt nauseous all day. I started shaking on 16 tee box and then just tried to get it in, really. Just wanted to get it in," he added.

The 27-year-old started Saturday having two bogeys in his first four holes and had a birdy in the 10^th.

Day again bogeyed in his 11^th hole and had two more birdies in the 12^th and 18^th hole playing the back nine in 4-under-par 31 which placed him in a four-way tie.

"Last year I didn't play the round after I had vertigo, and this one was worse. I think the goal was just to go through today and see how it goes," Day said regarding his current situation according to ESPN.

Meanwhile, Day's playing partner Kevin Kisner praised his great performance despite the health issue he is going through during the tournament.

"He played unbelievable. He didn't feel good at all. I told him I'd try to help him in any way I could. I asked him if he wanted me to pick his ball up out of the hole. He was struggling," Kisner said according to ESPN. "But there's that old saying, beware the sick golfer, and that kind of rang true today."

The US Open 2015 leaderboard can be seen by clicking here.

The US Open 2015 can be watched online through live stream by clicking here.