Kellett, who missed the cut in his only other appearance this year on the second-tier circuit, carded a flawless 69 on a sun-kissed day at Gloria Golf Club.
The three-under-par effort saw him jump 18 spots to joint-43rd on four-under after he’d made it to the weekend right on the cut.
“I was very solid all day,” said the 28-year-old Motherwell man. “I could have been really low as I gave myself 10 birdie chances from inside 15 feet.”
The ones he converted came at the second, 16th and 17th as Kellett leapfrogged Ferguson as well as Duncan Stewart and Bradley Neil.
“I’m not making many mistakes at the moment, which is pleasing,” he added. “There are lot of positives for me so far this week, with the only disappointment about today being that my score wasn’t lower.”
Ferguson’s delight at making the cut as an amateur was replaced by disappointment after he tumbled nearly 40 spots down the leaderboard following a 76.
“I played poor the whole day,” said the 19-year-old from Bearsden after a round in which the bulk of the damage was caused by four bogeys in a row from the 12th.
“I had struggled on the range before I went out, hit one in the trees at the first and just had a horrible day. It was not fun at all.”
That sentiment was shared by both Stewart and Neil after they signed for a 72 and 77 respectively.
Last weekend’s winner in Madrid, Stewart was out in four-under, having birdied the first two holes then chipping in for an eagle-3 at the ninth.
But the 31-year-old then saw that good work undone by back-to-back double-bogey 6s at 13th and 14th.
“I played really good for 14 holes today but no so good for the other four,” said Stewart. “That was a pity as it could have been a low one.”
Neil slipped to last among the 71 qualifiers after his five-over effort, which finished with a double-bogey 7.
A Frenchman is still out in front heading into the final round, but it is Clement Sordet rather than halfway pacesetter Matthieu Pavon.
As Pavon slipped to joint-third following a 71, compatriot Sordet took over at the top of the leaderboard with a 65 for 17-under.
He leads by two shots from Swede Sebastian Soderberg, who is out in front in this season’s Road to Oman, with compatriot Jens Dantorp a shot behind after a 64 that included a hole-in-one at the 15th.