Emerging midfielder Jack Sinclair has extended his contract with St Kilda by a further two AFL seasons.

The 22-year-old, who has re-signed to the end of 2019, has played 38 games with the Saints since his 2015 debut, including 11 this year.

He averages 21 disposals in 2017, having played every game since his round-six inclusion against Hawthorn in Launceston.

"It's a really exciting time to commit to the club for the next two years," Sinclair said in a statement on Wednesday morning.