McNealy, the son of a Silicon Valley billionaire, sits alongside fellow American Alex Smalley atop a bunched leaderboard which continues to feature some surprising names near the summit.

The pair are a shot ahead of Germany’s Stephan Jaeger – who had an unusual round of 18 pars – and South Africa’s rising star Aldrich Potgieter, although the presence of American Chris Gotterup, Japan’s former Masters champion Hideki Matsuyama and Australia’s Min Woo Lee – all in form on the PGA Tour this year – is far from leftfield.

Lurking below the frontrunners are a host of superstars eager to pounce at the weekend.

World number one Scottie Scheffler, fellow American Cameron Young and Sweden’s Ludvig Aberg are in a group on two under par, while Spain’s Jon Rahm is one under.

Three-time major champion Jordan Spieth – aiming to finally end a nine-year wait to complete the career Grand Slam – is alongside McIlroy at one over.

Given 58 players all within six shots of the lead the second men’s major of the season remains impossible to call.

Going into the tournament there was a lot of talk centering on how Aronimink could prove too easy for the world’s best given the last tournament held here, a PGA Tour event in 2018, which Keegan Bradley won on 20 under par, defeating Justin Rose in a play-off.

Even if bombed drives missed wide fairways, the belief was that players would be able to gouge wedges out of the thick rough onto greens and lead to a putt-off.

The PGA of America has responded by setting up the course in a manner which aimed to disprove that.

The rough has largely been penal for those who have been unable to keep the ball on the fairways, while the severity of the slopes on the greens have generally caused havoc, with more three-putts after two rounds than during the whole of the Masters.

However, McNealy was one player who bucked the trend on Friday. The 30-year-old former world number one amateur ranks joint 143rd – out of a 156-man field – with his driving accuracy – but has used his short irons superbly to launch a challenge.

“I think this is one of the few courses I can compete on without hitting enough fairways, I think the missed fairways penalty isn’t as bad as other places,” he said.

“Fairways are definitely easier to control the ball and I hope to hit more this weekend.”