The fine end-of-season campaigns being enjoyed by Australia’s top two men players, Alex de Minaur and John Millman, continued at the Sofia Open as the pair battled their way into the quarter-finals.

Millman, fresh from his first ATP Tour triumph at the Astana Open at the start of the month, defeated veteran Gilles Simon 7-5 6-7 (3-7) 6-2 to reach the quarter-finals of the Sofia Open.

Then De Minaur, the No.1-ranked Australian man, followed up with a 6-4 7-6 (7-5) victory in the second round over Russian Aslan Karatsev.

The 31-year-old Queenslander Millman again demonstrated his current confident form by prevailing against Simon who, in typically doughty fashion, saved four match points before eventually capitulating.

The sixth-seeded Millman had to overcome the disappointment of seeing the never-say-die 35-year-old save two of those match points before he went on to snatch the marathon 82-minute second set in a tiebreak.

Yet the Australian brushed aside the setback to earn another break at the start of the third set and go on to set up a last-eight meeting with Canadian Vasek Pospisil.

There was more defiance from Simon who saved two more match points when 5-1 down in the third set but, at the fifth time of asking, Millman was not to be denied as he ran out winner after three hours and 18 minutes.

De Minaur, the No.3 seed who has also been in good nick having reached the final of last month’s European Open in Antwerp, always looked to have the easier task against the world No.114 Karatsev but it was not a straightforward victory.

An immediate break to love smoothed De Minaur’s comfortable path to the first set but the Russian hit back to earn two set points in the second.

Once the 21-year-old Australian had rescued those and taken the set into a see-saw tiebreak, the pair eked out no less than nine mini-breaks between them before De Minaur finally sealed the win in one hour 52 minutes.