[4] He was signed to the Shrewsbury Town youth academy towards the end of the 2016–17 season on the recommendation of former Grimsby manager Paul Hurst.
[4] Sielis travelled with the Shrewsbury Town first-team squad to a training camp in Portugal, and featured regularly during the 2017–18 pre-season.
[6] In the same competition on 7 November at home to local rivals Walsall, he made a last-minute error that allowed the opponents to score the only goal of the game.
[7] On 21 September 2018, Sielis was loaned for a month to Halesowen Town in the Southern Football League Premier Division Central.
[8] He played five total games during his time in Worcestershire, and scored his first career goal from a long-distance run in a 3–0 win over Wolverhampton Wanderers in the Birmingham Senior Cup.