Rock and Mansell were among 20 players who posted a score of one under par to sit joint 15th, three shots off the lead jointly held by France’s Julien Guerrier, Scotland’s Connor Syme and England’s Dale Whitnell.
It could have been even better for the duo, who bogeyed their final hole of the day, the par-three 10th.
Rock – from Armitage, near Rugeley – had earlier shot a birdie at his opening hole, the 11th, as well as the second, fifth and ninth, while recording bogeys at the par-four first and eighth.
Mansell started and finished with a bogey, but in between he found birdies on the 15th, 18th and ninth.
The 10th also proved troublesome for Ludlow’s Oliver Farr as he finished one over par in a tie for 57th.
That was one five holes on which he recorded a bogey – but he also sunk birdies on the third, sixth, 11th and 15th.
Hawkstone Park’s Ashley Chesters had a topsy-turvy day that saw him record four birdies, three bogeys and a double bogey. he did manage to par the 10th though.
Whitnell was the only one of the leading trio to post a flawless round and he said: “It’s tough out there, the wind is swirling about which is making it extremely tough but I had a gameplan and managed to execute it.
“There are obviously tough holes out there so I just tried to be disciplined. Gordy has been great on the bag this week so we made some great decisions and I managed to execute the shots that I needed to.
“I just need to keep doing what I’m doing, keep grounded and try and clip off a few birdies here and there.”