Complex sentence: At the first round of 2015 US Open, Diyas was defeated by Polona Hercog 6-2,7-5; eventually failed to repeat her third round appearance in the previous year.
Split into simpler sentences: At the first round of the 2015 US Open, Diyas was defeated by Polona Hercog 6-2,7-5. This meant that she failed to repeat her third round appearance in the previous year.