Paris, France, 30 October 2018 | AAP

Australian young gun Alex de Minaur was unable to convert two match points before losing a three-set marathon to Feliciano Lopez at the Paris Masters.

Almost twice de Minaur’s age, the seasoned Spaniard showed his metal to fight back in the tiebreaker and triumph 6-7(4) 6-4 7-6(6) in their first-round clash at the ATP Masters 1000 event.

Earlier on Monday, John Millman’s season appeared to come to an end after being forced to retire during his first-round match against Nikoloz Basilashvili due to a back injury.

The US Open quarterfinalist has endured a steady stream of injuries over the years and seemed limited in his match against the hard-hitting Georgian.

The 29-year-old Millman was heard to say he was struggling to serve and received painkillers and strapping to his back when down 4-3 in the first set.

The Australian No.2 pulled the pin after dropping the set 6-4.

Lucky loser Matt Ebden remains the sole Australian left in the draw in Paris and will face Karen Khachanov for a spot in the last 16 after the Russian beat Filip Krajinovic 7-5 6-2.

Ebden, who lost in the final round of qualifying, replaced Kyle Edmund in the draw after the Brit withdraw due to a knee injury.

The 19-year-old de Minaur also battled physical woes, receiving treatment for a neck problem after winning the first set.

Lopez bludgeoned 19 aces to three but neither found it easy to make inroads on serve with only one break in the match.

After de Minaur saw off two match points at 4-5 in the third set, the Australian No.1 was on the brink of victory after racing to 6-4 in the deciding tiebreak.

But the 37-year-old Lopez reeled off four straight points to stop de Minaur in his tracks, winning a 16-shot rally to close out the match in just under three hours.

He next plays Argentinian 15th-seed Diego Schwartzman.

Millman missed much of 2017 through injury but has had a strong 2018, moving up to world No.35.

He defeated Roger Federer to reach the last eight at Flushing Meadows, made the final of the Hungarian Open in April and was recently short-listed for ATP comeback player of the year.

But pickings have been slimmer since his remarkable US Open, winning just the one match in his past four tournaments.