Jessica Pegula is through to the Adelaide International semi-finals after Ashlyn Krueger retired through injury.

The pair faced off in an all-American quarter-final before Krueger called for her trainer in the second set and subsequently retired due to a right thigh injury.

Pegula, playing her first tournament in 2025, had made a strong start and led 6-4 2-0 before the match ended.

"It's never fun to win with a retirement," said the top seed.

"I knew she had a tough singles [on Wednesday]. But coming out you never know what to expect. She was still playing amazing tennis."

Pegula, looking to reach a first final since her US Open defeat to Aryna Sabalenka last year, will face Yulia Putintseva, who beat Diana Schnaider in three sets, in the final four.

Elsewhere, number two seed Emma Navarro was stunned by Liudmila Samsonova in their quarter-final meeting as she lost in straight sets.

The Russian cruised to a 6-4 6-4 victory, earning her first top 10 win since beating Elena Rybakina in Beijing in 2023, where she went on to make the final.

She will face Madison Keys after her straight-sets win over Daria Kasatkina.