The signs are good that Olympic champion Mack Horton will overcome underwhelming trials form and regain his mojo at this week’s world swimming titles in South Korea. Australian head coach Jacco Verhaeren is confident Horton will bounce back to his best at the eight-day world titles starting at Gwangju on Saturday after some scorching training times.

Horton only made the 27-strong Dolphins’ world titles squad thanks to Verhaeren’s discretionary powers. The Rio 400m champion was set to feature only in the 4x200m relay team after bombing out in his pet event and also missing selection for the 200m and 800m freestyle at last month’s trials in Brisbane.

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However, Verhaeren threw Horton a lifeline and confirmed him as a starter in the 400m and 800m freestyle at Gwangju, putting him on a collision course with controversial Rio sparring partner Sun Yang of China. And after witnessing Horton respond at training since his bold call, Verhaeren is confident the 23-year-old will be back to his best sooner rather than later.

“I think he has made a good shift already,” Verhaeren told AAP. “He is training well. We are confident. He is the Olympic champion and he wasn’t happy with his trials time. But definitely so far so good. We are expecting a [form] shift here.”

Horton failed in his bid to qualify in the 200m, 400m and 800m at the trials but still had his name read out with the Dolphins team. Yet Verhaeren backed Horton to come good in South Korea, claiming the gold medallist found it hard to adjust to his training program since ditching his beloved 1500m freestyle last year.

“It’s difficult. I don’t think it [trials form] was a mental thing. It was probably him still adjusting to his change in training intensity after focusing on 200m and 400m,” Verhaeren said. “Sometimes it takes a while before athletes digest a change in program.”

Horton’s selection reprieve again puts him in the sights of Sun, who the Australian famously dismissed as a “drug cheat” before upsetting the Chinese gun in the Rio Olympic 400m final. Sun avenged that shock loss when he relegated Horton to 400m silver at the 2017 world titles.

But Verhaeren was quietly confident Horton was up for round three at Gwangju after Sun was sensationally cleared to compete at the world titles following a delay in setting a date for his latest doping case

Sun – who served a secret three month doping ban in 2014 – faces a lifetime suspension after allegations a vial of his blood was smashed by a hammer during a clash with testers in China last year.

“Hopefully it [form] kicks in for the world champs and if not we will have information to work with for Tokyo,” Verhaeren said of Horton.