Adelaide United have agreed a deal to sell captain Dylan Holmes to Swedish champions BK Hachen, despite being three games away from a W-League finals campaign.

Holmes will play in third-place Adelaide's Saturday night clash with table-topping Sydney FC before packing her bags to pursue her European dream.

Losing the central midfielder, who has been an ever-present for the Reds since the start of the 2018-19 season in her second stint at the club, is a setback with finals just around the corner.

But it was a move the 23-year-old couldn't resist.

"Probably one of the hardest decisions I've made in my career," Holmes said.

"But the opportunity to play in Sweden and really test myself in a very strong European league is something I couldn't turn down."

As well as helping Hachen defend their Damallsvenskan title, Holmes will also get a chance to play for the club in the 2021-22 Champions League campaign where she could face fellow Australians such as Lyon's Ellie Carpenter, Chelsea's Sam Kerr and Arsenal's Caitlin Foord.