The Lightning signed goalie Evgeni Nabokov in the offseason in part so the veteran could mentor prospect Andrei Vasilevskiy.
Seven months later, Vasilevskiy is taking Nabokov's spot as the backup goalie.
The Lightning has placed Nabokov on waivers and called up Vasilevskiy from Syracuse on Sunday.
"We decided we wanted to give him more games," Lightning general manager Steve Yzerman said of Vasilevskiy. "We didn't feel it was right for Evgeni or the team to kind of keep him here if he's not going to play."
Nabokov came to the team as a proven veteran and is three games shy of reaching the 700-game milestone across his 14 NHL seasons. He was 15-14 with a 2.74 goals against average in 40 games with the Islanders last season.
While popular in the locker room, Nabokov struggled to adapt in his first year as a backup, to Ben Bishop. The 39-year-old Russian was 3-6-2 with a 3.15 goals against average in his 11 games with the Lightning. His save percentage (.882) was the third-worst in the league among goalies with at least 10 games, and he appeared in only two games since Christmas.
Yzerman said he told Nabokov of the move after Saturday's 3-1 win over Columbus but politely declined to reveal their conversation or speculate on what might happen if Nabokov clears waivers.
"Nabby's a really good guy," Yzerman said. "He's a professional."
Vasilevskiy, meanwhile, left a strong impression in his brief time with the Lightning. The highly touted 20-year-old Russian won three of his first four NHL starts. He posted a 1.76 goals against average and a .937 save percentage during his previous two stints with Tampa Bay in December while still adjusting to the North American game.
"He's handled it well…" Yzerman said. "He's been very mature about it, recognizing, hey, I've got some work to do, and I'm determined to get better and improve as quickly as possible."