Vehviläinen, 24, has played in one game for the Blue Jackets this season – his NHL debut on March 6. He's also suited up for one contest with the AHL's Cleveland Monsters and 13 with JyP Jyvaskyla in Finland's Liiga in 2020-21, where he went 3-7-3 with a 3.18 goals-against average and a .890 save percentage.
The Jyvaskyla, Finland native was a sixth-round pick (173rd overall) of the Blue Jackets in 2018 and backstopped the Monsters in 33 games during the AHL's 2019-20 season (10-18-4, 2.76 GAA, .901 SV%).
Lehtonen, 27, signed a one-year, entry-level deal with the Maple Leafs in the off-season and had three assists in nine games for Toronto this season. The Turku, Finland native will join the Blue Jackets taxi squad after obtaining a work visa and clearing quarantine.
Before signing in Toronto last May, Lehtonen posted a 17-goal, 49-point season in 60 games with Jokerit in 2019-20, which led KHL defencemen that season.