Lehtonen, 26, was recalled by Atlanta on Tuesday after completing a conditioning assignment with the Chicago Wolves of the AHL. The Finnish backstop has not played this season after undergoing back surgery on Sept. 16.
Over four seasons with the Thrashers, Lehtonen compiled a record of 94-83-17 with 14 shutouts. He led Atlanta to the franchise's only playoff appearance in 2006-07.
"We get a goaltender. That gives us three now, so that's a situation that we'll have to deal with," Stars head coach Marc Crawford told reporters on Tuesday night.
"Obviously I think they feel pretty good about Kari Lehtonen. He's come back and I've heard that he's played well at the American League level, so we'll see what happens from there on our side."
Lehtonen was originally drafted by the Thrashers with the second pick in the 2002 draft, after the Columbus Blue Jackets drafted Rick Nash first overall. He is completing the final year of a two-year, $6 million contract, and will become a restricted free agent at the end of the season.
Vishnevskiy, 21, was drafted by the Stars in the first round (27th overall) in the 2006 draft. The defenceman has spent the past two seasons shuttling between Dallas and the AHL. In five NHL contests, Vishnevskiy has two assists and two penalty minutes. He has eight goals and 16 assists in 51 games this season with the Texas Stars of the AHL, and is in the second year of a three-year entry-level contract.
The Thrashers are expected to assign Vishnevskiy to Chicago (AHL).