FN’s 2026 Flames summer prospect rankings – #10: Theo Stockselius

When he was selected by the Calgary Flames in the 2025 NHL Draft, the thought was that Swedish-born centreman Theo Stockselius was a bit physically under-developed due to some medical issues he had a few years back.

While he hasn’t quite had the chance to show his full potential quite yet, as his 2025-26 campaign was cut a bit short – pun not intended – by an early season skate cut to his leg that took him out of the lineup for a few months, he’s shown enough flashes of brilliance to give Flames brass, and fans, reasons to be excited for his development.

Stockselius cracks the top 10 of our annual prospect countdown, checking in at 10th spot.

Theo Stockselius

Forward; shoots left
Born July 24, 2007 (age 19) in Norrtälje, Sweden
6’3″, 196 pounds
Drafted in the second round (54th overall) by Calgary in the 2025 NHL Draft

A product of Norrtälje, a town northeast of Stockholm, Stockselius came up in local minor hockey a couple years behind his older brother, Lucas. He moved to play with IFK Täby HC in 2021 in a suburb directly north of Stockholm, where he played for two seasons. Notably, Stockselius performed well and dealt with a thyroid cancer scare during this period – when he was 15 – but he persevered, missed a few weeks of hockey, and then returned to action and made a full recovery.

In 2023-24, as a 16-year-old, Stockselius continued moving up the ladder, joining the Djurgårdens IF system in Stockholm proper. He had 39 points in 22 games in the J18 Region (the lower U18 division) and 24 points in 15 games in the J18 Nationell (the top U18 division), and had a point in two J20 Nationell games, too.

In 2024-25, as a 17-year-old, he had 4 points in 1 J18 Region game and 10 points in 5 J18 Nationell games, but he spent most of his time in the J20 Nationell, posting 51 points in 40 games. He managed to win the playoff tournaments in both leagues, spending the post-season moving between both the J18 and J20 Nationell tournaments simultaneously. Internationally, he also represented Sweden at the Under-18 World Championships and the Junior A World Challenge, winning silver at each event. He showed well enough to earn a second round selection by the Flames in the 2025 NHL Draft.

In 2025-26, as an 18-year-old, he had a shorter year. He suffered a skate cut to his leg on Oct. 9 against AIK’s U20 team that kept him out of the lineup until Jan. 15. As a result, he missed out on a pretty strong opportunity to play at the World Juniors. When he returned, though, he played just twice before Djurgardens’ senior team in the SHL was short players due to a slew of injuries and pulled him into action. From his return from injury until the end of the regular season, he actually played just four U20 Nationell games and 11 SHL games, bouncing between the top line in the U20 and the bottom six in the SHL, two very different roles.

He was fine in the SHL, playing a solid if unspectacular brand of two-way hockey in a limited role. When he returned to the U20 level, it was in the middle of the playoffs, and he played a big role in Djurgardens’ under-20 team winning the playoff tournament for the second consecutive season – he was named the playoff tournament’s MVP. Stockselius didn’t play a ton in 2025-26, but he showed that he can provide value to a team in both a big role and as a depth piece.

Expectations for 2026-27

Stockselius signed his entry-level contract with the Flames in early May. In July, it was confirmed by the Flames, and later by the Swedish club, that Stockselius would spend the 2026-27 on loan to Djurgardens – likely playing on their SHL team. The gist of it is that he’s entering his 19-year-old season, and his NHL deal would slide for the year. So he gets to spend one more year with his familiar club team, Djurgardens gets his services for one more season, and the Flames get him under contract and have a clock on when he’ll arrive as a full-time North American player (e.g., in 2027-28, for his 20-year-old season). Everybody wins.

For the upcoming season, he’s likely to be playing a bit more of a prominent role in the SHL – middle six rather than bottom six, probably – but just the experience of playing consistent high-end pro hockey will be invaluable for him as he moves forward. He’ll also likely be a big piece of Sweden’s World Junior entry, as he drew rave reviews for his performance at the recent Summer Showcase event.

Most importantly, we’re hoping Stockselius can stay healthy. He’s the type of player whose game could grow by leaps and bounds if he gets a bunch of reps this season. We’re hopeful he can get a ton of ice time – and growth – into the upcoming campaign.