Olympics-Swimming-Paltrinieri fastest in 1,500m heats, surprised by Sun Yang exit

* Italian sets pace ahead of American duo * Regrets from Sun Yang as defending champion struggles * Exit ends prospect of new showdown with Mack Horton By Mark Trevelyan RIO DE JANEIRO, Aug 12 (Reuters) - Gregorio Paltrinieri of Italy set the fastest time on Friday in qualifying for the final of the 1,500 metres freestyle and voiced surprise at the shock exit of defending champion Sun Yang, who ended his Olympics on a disappointing note. Americans Conor Jaeger and Jordan Wilimovsky qualified second and third for Saturday's final of the gruelling 30-lap event, the most arduous in the pool. The main talking point, though, was the poor showing by Chinese world record holder Sun, who toiled his way through his heat in the 16th-fastest time, more than half a minute off his best. Only eight go through to the final. "I saw the race in the call room. I mean it was a surprise, the 1,500 for Sun Yang. Since last year, when he missed the (world championship) final, we didn't know his condition in the 1,500," Paltrinieri said. "I'm sorry for him but I'm happy to be in the final," he said, smiling broadly. "I think his preparation is more in the 200 and 400, maybe." Sun blamed fever and flu medication for his poor showing. He swam in the same heat as Australia's Mack Horton, who beat him in the 400m on Saturday after describing him as a drug cheat because of a past suspension, a comment that prompted hundreds of thousands of Chinese Internet users to bombard Horton with demands for an apology that was not forthcoming. Asked about Sun's absence from the final, Horton said: "It doesn't really matter if he's there or not, to be honest. Just doing my own thing." He said he had not been paying much attention to the furore over his comments. "The Olympic Village is kind of like a bubble and you just stick to your own sort of thing in your little tower, basically." Paltrinieri clocked 14 minutes 44.51 seconds, beating Jaeger by 1.23 seconds in the fastest of the six heats. Sun's world record, set when he won in London in 2012, is 14:31.02. Sun, also champion at 400m in London, had been considered a certainty for the final. He has already won a gold in the 200m freestyle and silver in the 400 this week. Asked to sum up his performance in Rio, he told reporters: "There were happy moments but there were also regrets." (Editing by Clare Fallon)