The 17-year-old made his first team debut in May as he came off the bench to face NK Zagreb and is viewed as a top-future Croatian international prospect, having appeared eight times for the under-17 side.
Boss Slaven Bilic is hoping to use his Croatian connections to bring in Magnajic, although he won’t be immediately brought into first team contention.
Some reports say Serie A club Fiorentina are also keen to sign Magnajic but Bilic is determined not to miss out.