Stockholm, Sweden, 16 October 2019 | tennis.com.au

Big-serving Australian young gun Alexei Popyrin has guaranteed himself a career-high ranking after he fought his way into the second round of the Stockholm Open.

The 20-year-old served up 19 aces on his way to a 7-6(6) 7-6(5) win over German lucky loser Oscar Otte, who delivered 15 thunderbolts of his own in a match that lasted just under 90 minutes.

Popyrin, who had to come through qualifying to reach the main draw, will move up at least four spots to world No.86 after his first-round victory but faces a tough ask next against fourth-seeded Canadian Denis Shapovalov for a place in the quarterfinals.

Qualifier @AlexeiPopyrin99 stays winning!

The Aussie clinches his third win in as many days in Stockholm against lucky loser Oscar Otte 7-6(6), 7-6(5).#SthlmOpen pic.twitter.com/UerGvCeEvy

— Intrum StockholmOpen (@IntrumSthlmOpen) October 15, 2019

Earlier on Tuesday, world No.52 John Millman lost to Spanish fifth seed Pablo Carreno Busta.

Millman was unable to convert any of four break points against the world No.35 on his way to a 6-4 6-3 defeat in the Swedish capital.

Carreno Busta’s next opponent is Italian lucky loser Gianluca Mager, who recorded his first tour-level ATP victory 5-7 6-1 6-1 over Pablo Andujar.

At the WTA Kremlin Cup in Moscow, Ajla Tomljanovic went down in the first round to in-form qualifier Varvara Gracheva.

Gracheva, who won back-to-back 60K ITF tournaments before next winning three matches in Moscow qualifying to reach the main draw, extended her winning streak to 14 matches with a 6-3 6-2 win over the Australian.