Qiúduì shīqù le duìzhǎng, shèngxià tā gūjūn-zuòzhàn.
After the team lost its captain, he was left fighting on his own.
Tips
history
Recorded in the Sui-dynasty 《隋书·虞庆则传》, originally describing the general Yu Changru fighting an isolated battle (由是长儒孤军奋战，死者十八九). The military image carries straight into modern figurative use.
usage
Often used self-deprecatingly or sympathetically - describing someone overworked because their team or backup never showed up. Compare 单打独斗, which leans more on "deliberately solo" rather than "abandoned."
