Scot Marc Warren had a three-over-par 73 in his first ever major round and said: "It was everything I expected and more."
"It was a rollercoaster ride. I hit some good shots which brought me rewards and bad shots which got punished.
"There aren't really any European Tour events which can prepare you for how tough this is - hence why they call it the toughest test in golf.
"It's a fair test, though. You have to shape your tee shots accordingly, and you can't afford to get too aggressive with your iron shots - even from the fairway - or with your putts.
"So it's a steep learning curve, but I'm loving every minute of it. The crowds are great.
"The aim first and foremost is to make the cut. As the old saying goes, you can shoot yourself out of the tournament on the first day, but you can't win it."