The man from the Belfry rung up five birdies on the bounce at the start of his round before taking his foot off the pedal and finishing with a seven-under-par 63 for a four-way share of the lead.
Rock, wearing his trademark red shirt, was on a roll from the moment he boxed a short putt at the 10th, his first hole, and then proceeded to pepper the flags with some brilliant approach play.
Surprisingly, despite figuring in the upper levels of the game in recent years - most notably when he tied fourth in the 2003 British Masters - he's still looking for his first victory.
And if he achieves it on Sunday, in a tournament for which the MEN is media partner, he'll be well on the way to regaining the full European Tour card he lost last year.
Rock said: "I got out an old driver out I used in the Open at Royal Liverpool in 2006 and I seem to have picked up an extra 10 or 20 yards.
"Up to this week I've been hitting the ball nicely and maybe not hitting many putts but I holed quite a few to start with so that made me feel better."
Also log-jammed at the top of the leader board are great Dane Kasper Linnet; Swiss player Raphael de Sousa and Scotland's Ritchie Jorgensen.
Breathing down their necks is David Horsey who fired a bogey free 64 then admitted he was not happy with his swing.
"It just doesn't feel right and it hasn't for a few weeks," said the 22-year-old rookie professional from Styal.
"But I holed a long putt at the first for a birdie and that set the pattern for the day."
Horsey, playing with former Ryder Cup star Andrew Coltart and Gary Emerson, had plenty of local support to encourage him and he's expecting more this weekend.
"It was great to see so many from my club," he said as he made an impressive start to win his maiden tournament for his grandmother who died on Monday.
"That was always at the back of my mind but I still kept up my concentration on my game," he added after fifth other players matched his score.
In perfect conditions, 91 players out of 156 were under par. Among them was John Cheetham with 68 on his Challenge Tour debut - then headed to the putting green.
"I missed four chances from eight feet in my first five holes so I know the part of my game I need to work on," said the 23-year-old assistant at the host club who is tied 74th.
Cheshire amateur Adam Wills, from Sandiway, whose dad David is professional at Portal, also returned a well crafted 68, moving to three-under-par before giving back a shot at the long 14th.
Swinton Park assistant David Smith rued three putting the 17th from a few feet then missing from little more than a yard on the last as he came in with a 69. He shared the mark with Didsbury's David McKinnon, hoping to make the cut as he did last year.
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