GREATER Western Sydney has added an extra first-round pick - No.16 as it stands - for losing free agent Harry Perryman to Collingwood.

The Giants' compensation comes after St Kilda was also granted Band One compensation - pick No.8 - after defender Josh Battle's departure to Hawthorn. GWS now has picks No.15 and 16 in the first round of the Telstra AFL Draft. 

INDICATIVE DRAFT ORDER What picks does your club have?

After being chased by Hawthorn, Port Adelaide and the Pies, Perryman this week decided on the 2023 premier as his new home.

The free agency move was confirmed on Friday.

The AFL's compensation formula for clubs who lose a free agent has long been shrouded in some mystery, although a player's age and salary and the length of the contract are contributing factors. 

Perryman played 129 games for the Giants in eight seasons.

The 25-year-old's shift south follows that of teammate Isaac Cumming, who will join Adelaide on a six-year deal.