Petra Marcinko completed a remarkable late-season surge as singles and doubles victories at the prestigious Orange Bowl Junior Tennis Championships saw her climb nine places to finish as the year-end junior world No. 1.

The 16-year-old Croatian fended off two rivals for the top spot in the girls' rankings in the process, beating Linda Fruhvirtova in the quarter-finals and doubles partner Diana Shnaider 3-6 6-1 6-3 in the title match at the JA Plantation tournament to secure her third junior singles title of the year.

“It was so unexpected. It feels amazing,’’ Marcinko told the Miami Herald. “Last year I lost in the first round, so winning this match is really difficult. Every match is like a battle so all together I feel really good.”

Marcinko’s ranking surge was boosted by the fact that she also won the doubles title with Shnaider, who was able to put her singles defeat to one side as the pair teamed up to beat the Fruhvirtova sisters, Brenda and Linda, 7-6(5) 6-0 for their second successive doubles title.

The victory was a repeat of their triumph at the J1 Bradenton (Eddie Herr) tournament the week earlier, when they edged past the Fruhvirtovas in a deciding match tie-break.

With her twin triumphs, Marcinko became the first girl to win both the singles and doubles titles at the under 18 Orange Bowl since 1993 (since doubles records were kept), though she was more concerned with the oddity of facing her friend and doubles partner for the biggest win of her fledgling career.

“That was so weird,’’ Marcinko admitted. “It didn’t feel like it’s a real match, I feel like it’s practice, and then after I realised I’m in the final right now.”

Finishing as the year-end world No. 1 caps a fine season for the Croatian, who also won the singles and doubles titles at JA Cape Town as well as the singles at J1 Lambare, and achieved a quarter-final finish at the US Open.

The boys' event also saw a slice of history as Adolfo Daniel Vallejo became the first Paraguayan to win an Orange Bowl title following his 6-2 6-3 triumph over American Bruno Kuzuhara. 

Vallejo, who is coached by Paraguayan former world No. 52 Ramon Delgado, claimed his first title of the year as a result - and is confident that the win will be well-received in his home country.

"It will be a big deal," Vallejo told Zoo Tennis. "In Paraguay we love tennis. We don't have basically any players right now, and it's a long time since Victor Pecci reached the final in the French Open, so yeah, it's a big thing for Paraguay. I'm very proud."