[3] Following the success of the academy side, in July 2019, van Poortvliet was one of 11 players offered professional terms to join the club's development squad.
[4] He made his first team debut for Leicester on 21 September 2019 in a Premiership Rugby Cup match against Worcester Warriors at Sixways.
[5] On 21 February 2020, van Poortvliet made his full Premiership debut in a 36–3 defeat to Sale Sharks at the AJ Bell Stadium in Salford.
[6] He scored his first try for Leicester against Harlequins on 13 February 2021, which won the "try of the week" award for that round of the Premiership Rugby season.
On 30 October 2021, van Poortvliet scored two tries after appearing as a substitute in the East Midlands Derby against Northampton Saints.