The Sharks also received a fifth-round pick in the 2022 NHL Draft.
"I had no idea. I was actually on the ice," Kahkonen said. "They pulled me out of morning skate and told me I had to leave the ice, and at first I was kind of thinking something happened to someone in my family or something but so I was scared. ... Obviously, it was a shock at first but now that I've had a little bit of time here to think about it, I think it's going to be a great opportunity."
The 25-year-old goalie is 12-8-3 with a 2.87 goals-against average and .910 save percentage in 25 games (23 starts) this season. Selected by the Wild in the fourth round (No. 109) of the 2014 NHL Draft, Kahkonen is 31-17-4 with a 2.89 GAA, .907 save percentage and two shutouts in 54 NHL games (51 starts).
He is in the final year of a two-year contract he signed Oct. 12, 2020, and can become a restricted free agent after the season.
"It wasn't anything just to address what's going on now with the injuries," Sharks assistant general manager Joe Will said. "It's really about looking forward, and we had the opportunity to acquire a 25-year-old up-and-coming goaltender. And that's a player we looked at quite extensively through expansion last year."
Kahkonen joins goalies James Reimer, Adin Hill and Zach Sawchenko on the Sharks roster. Reimer is 16-13-6 with a 2.80 GAA, .916 save percentage and one shutout in 37 games (36 starts).
Hill is out with a recurrence of a lower-body injury. He made 29 saves in a 5-0 win against the Los Angeles Kings on March 12, his first start since Jan. 22 after missing 15 games. Reimer missed four games from March 1-15 with a lower-body injury.
"All I know is right now, is since January we've had one of our big two [goalies] out consistently," Will said. "When we looked at it, we didn't have that depth at the goaltending position. That really drove our decision."
Kahkonen said he hopes to join the Sharks for their game at the Calgary Flames on Tuesday (9 p.m. ET; SN1, NBCSCA, ESPN+, NHL LIVE).
"Everyone who has called me has been really welcoming," Kahkonen said. "It seems like everyone -- a lot of great people. So I'm excited to get going here."
Middleton, a 26-year-old defenseman, scored nine points (three goals, six assists) in 45 games for the Sharks this season.
Selected by the Los Angeles Kings in the seventh round (No. 210) of the 2014 NHL Draft, Middleton has scored 12 points (three goals, nine assists) in 59 NHL games, all with San Jose. He is in the final season of a two-year contract he signed Oct. 5, 2020, and can become a restricted free agent after the season.
"Everybody here as an organization, every single person on the staff, and players, thinks the world of 'Midds' and just wants to really thank him for what he's done and he'll be missed," Will said. "We went into this deadline here not really going out and shopping him per se, but he was a player that teams wanted."
Also on Monday, the Wild acquired goalie Marc-Andre Fleury in a trade with the Chicago Blackhawks for a conditional first-round pick in the 2022 NHL Draft. The Sharks acquired defenseman Anthony Bitetto from the New York Rangers for forward Nick Merkley.
NHL.com independent correspondent Chelena Goldman contributed to this report
