The 19-year-old Eklund was San Jose's seventh pick in the draft this year and quickly showed signs of why the Sharks believe he will be a foundation player for the future.
Eklund had four assists in nine games and didn't look overmatched in his first stint in the NHL.
But the Sharks still opted to send him back to Djurgardens IF in Sweden before he played his 10th game, which would have triggered the first year of his three-year entry contract.
"This was one of the toughest decisions we have had to make," general manager Doug Wilson said. "William's tremendous skill and vision have been evident since his participation in our rookie tournament in September. In his nine NHL games as a teenager, he has shown that he is going to be a special player in this league, but ultimately, we feel it is in the best interest of his long-term development to return to Sweden and continue to work on becoming the dominant player we know he can be."
Eklund played mostly on the top two lines and handled the tough competition well for a teenager. His play impressed his older teammates.
"He's going to be an elite player in this league," captain Logan Couture said. "It's tough to play in this league at 18, 19. He's shown he can do it. Very impressive. It isn't easy to do what he's doing, playing top-six minutes. ... He proved he can play in the NHL."