World number one Novak Djokovic remains without an ATP Tour title this season after losing to Russia’s Andrey Rublev in the final of the Serbia Open.

Djokovic fought back from a set down for the fourth time this week in front of his home fans in Belgrade, but ran out of steam in the decider as Rublev powered to a 6-2 6-7 (4) 6-0 victory in two hours and 29 minutes.

It was Rublev’s first win over a world number one and gives the 24-year-old a third tour-level title of the season – equalling the tally of Rafael Nadal – following previous victories in Marseille and Dubai in February.

Rublev broke Djokovic’s serve twice in the opening set and saved five set points in the second to force a tie-break, but Djokovic roared into a 5-2 lead and let out a roar of delight as he levelled the contest.

However, the efforts of the week then seemed to catch up with Djokovic and Rublev broke his opponent’s serve three times to storm through the decider without losing a game.

“It is big to play against you and share the court for the second time,” Rublev said to Djokovic during the trophy ceremony.

“I hope we have more battles. I feel so great here, it is a very nice city. It feels really special. I want to say a big thanks to all the spectators for supporting all the players all week. To see full crowds again is special for all of us.”

Carlos AlcarazSpain’s Carlos Alcaraz holds the trophy after winning the Barcelona Open (Joan Monfort/AP)

Spain’s Carlos Alcaraz had more luck on home soil than Djokovic, the brilliant teenager defeating compatriot Pablo Carreno Busta 6-3 6-2 to win the Barcelona Open.

Alcaraz, who has now won three titles this season, is projected to reach ninth in the world rankings on Monday, making the 18-year-old the youngest player to crack the top 10 since Rafael Nadal did it 17 years ago after lifting his first Barcelona trophy.

“It means a lot,” Alcaraz said in his on-court interview. “I’ve watched this tournament since I was a kid. I always wished to play in this tournament and of course to be able to win this tournament.”

While the final was a relatively routine affair, Alcaraz had earlier saved two match points in his semi-final against Alex De Minaur, which had been delayed until Sunday due to rain.

On the first match point De Minaur had the chance to put away a short forehand to seal the win, only for Alcaraz to produce a brilliant passing shot down the line having seemingly overrun the ball.

Alcaraz eventually prevailed 6-7 (4) 7-6 (4) 6-4 after a contest lasting three hours and 40 minutes.