Konta, 28, meets seventh seed Sloane Stephens, last year's runner-up, in Tuesday's quarter-final at 13:00 BST.

The Briton had never won a main-draw match at Roland Garros until this year.

"A lot of things are coming together but she can go up a few more levels if pushed," Keothavong told BBC Sport.

"Jo has played some fantastic tennis and the best thing is she can play even better - she is still very much playing within herself."

Konta, seeded 26th, only claimed her maiden first-round victory on the Paris clay against German qualifier Antonia Lottner last week.

The former world number four fought off sickness to battle past American Lauren Davis in the second round, then eased past young Slovakian Viktoria Kuzmova and Croatian 23rd seed Donna Vekic to reach the last eight.

Now she is bidding to compete in her third Grand Slam semi-final after reaching the same stage at the 2016 Australian Open and Wimbledon in 2017.

'Fed Cup success has helped Konta'

Former British number one Durie - the last woman to reach the Roland Garros last four - says she would be "very happy" for Konta if she emulated her feat.

"Johanna has worked out a way to use her game on the clay to really good effect," Durie, 58, told BBC Sport.

"She's worked very hard to get back to this kind of standard."

After little previous clay-court pedigree, Konta has enjoyed surprise success on the surface having also reached two WTA Tour finals at the Morocco Open and Rome Masters going into Roland Garros.

That came after she helped Britain win promotion to the Fed Cup World Group II stage - which Durie believes has boosted Konta's mental toughness.

Konta has won 13 of her 15 three-set matches this year, including a victory over American Stephens on clay in Rome.

"I think the whole team atmosphere at the Fed Cup worked very well and she won some really tough three-set matches," former world number five Durie added.

"I think that has helped her so much mentally and for her to take so many three-set matches this year."

'Open draw gives Konta great chance'

Stephens is one of only three top-10 seeded players left in the women's draw, along with Romania's defending champion Simona Halep and Australian eighth seed Ashleigh Barty.

Konta and Barty are among five players in the Roland Garros quarter-finals for the first time, along with 17-year-old American Amanda Anisimova, Croatian 31st seed Petra Martic and Czech teenager Marketa Vondrousova

Keothavong believes Konta can take advantage of an open draw and go on to win the tournament.

"Any one of these players still left in the draw has a good shot at it," she told BBC Radio 5 live.

"She is playing with confidence and it has been building over the last few weeks.

"She has performed very well and this has been her best season by a country mile on clay.

"With each match she is looking more and more comfortable."

Along with the victory in the Rome second round, Konta also beat 2017 US Open champion Stephens in straight sets on the hard court at the Brisbane International in January.

Stephens says those two defeats will have no bearing on the encounter in Paris, insisting she will go in with "a clean slate".

"When I played her in Brisbane it was the first match of the year, so that's totally out of my mind," said Stephens, who lost to Halep in last year's final.

"And then the one in Rome, bad circumstances. Out of the mind."